Possible Control Module Problem - Blower Motor Wont Turn Off

dgreen

Original poster
Member
Jan 22, 2012
6
Hello Everyone... I am hoping some of you may be able to help me.. And yes I have done research and tried some suggestions.

Truck: 2006 Trailblazer LT w/ Auto Climate Controls

Issue: The other day after returning home and exiting the vehicle, the blower motor continued to run even without the key being in the ignition. I researched potential problems on Trailvoy and Google and it seemed the potential problem was the Blower Motor Control Module.

I went to O'Reilly Auto Parts and purchased the Blower Control Module (Part # BWD RU1321). This part matched a 2005 Trailblazer w/ Auto controls but they did not show anything for a 2006. After they did a little research, they said that this was compatible with my truck as well. They also referenced my old part that came off the vehicle. It looks just like the AC Delco part on ebay and around the internet. (It has the new 5 pin connector)

So this is the new 5 pin connector that requires me to cut off my old 3 pin connector and hard wire the new control module wires into it. No Problem.. So I perform the install and it worked right away with the key in the ignition on accessory, but when I started the truck, it stopped working. Then it came on again a few minutes later while driving, but stopped working when I turned off the truck and back on again. Figuring it was a fluke, I exchanged the part for another one and I still have the same problem.

I checked it with my Volt Meter and it shows power going to the module. It also shows power from the wire that goes to the blower motor and the voltage increases & decreases volts as I turn the speed up & down on my Auto HVAC control.

I guess Im just confused as to what the problem could be. Is the part I bought from O'Reilly just not as good as an AC DELCO or GM replacement part? I am expecting the blower to turn on almost immediately after I start my truck not minutes later or only work intermediately.

Any help, suggestions, ideas or anything else would be greatly appreciated, as I am trying to avoid going to the dealership for repair.

 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
dgreen said:
... I am expecting the blower to turn on almost immediately after I start my truck not minutes later or only work intermediately..
Welcome! Glad you found your way over here. :wink:

That replacement module shouldn't be such a dog. I'd look into the wiring a bit more. You have to catch it in the act of failing, then find the issue with your meter. If the main input red wire never loses power, then the fuse and fuse block wiring is OK. That red wire is always hot, even with the ignition off, which is the reason a bad module can cause the fan to run on and drain the battery even with the key out. The other function some folks skip checking is the black wire ground input. If you're checking the voltage on the wiring, you may have put your low side meter lead on a sheet metal ground elsewhere. When the motor fails to run, check the orange wire going to the motor for voltage, but then also check the black lead to make sure there's zero volts on it when measured to a sheet metal ground. If the black wire jumps up to be the same voltage as the orange, then the ground to the module is flaky. That could cause your symptoms.

Also wiggle the connector going into the motor to make sure the contacts aren't slightly oxidized on the motor side, even though the ones on the module side are fresh. That happens a lot, and causes the most common blower fault which is overheated and melting connector bodies.

For an emergency power path to bypass the module if you can't find the root cause right away, splice in a SPST switch (using 3M tap connectors) from red to orange.

I assume you don't need the schematic - just post up if you do. It's simple.
 

dgreen

Original poster
Member
Jan 22, 2012
6
Roadie - Thanks for the quick response. I am going to do some testing now. I will post my findings shortly.

Ok... So there seems to be constant voltage from the red input wire when the fan is off or on. There also seems to be voltage on the input ground wire weather the fan is on or off but its only like .23 volts so not even a full volt. I grounded the + from my meter to a screw on the truck and I got the voltage on the ground wire but I didn't seem to get any voltage when grounding to sheet metal I had in the garage.

The plug that goes to the blower motor is getting volts and adjusts volts as I increase and decrease the the speed on my hvac unit. I don't know how I can test the blower motor wires when the blower fan is pluged into the motor to read the volts when the fan turns on or when it won't turn on...

Any ideas from my findings.

Also, when I put my head near the blower motor and disconnect the input ground wire from the car to the module and quickly tap them together, I hear a clicking sound that seems to be coming from the blower motor. About 1 out of 5 times the blower motor turns on.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
dgreen said:
Ok... So there seems to be constant voltage from the red input wire when the fan is off or on.
That's as expected.
There also seems to be voltage on the input ground wire weather the fan is on or off but its only like .23 volts so not even a full volt.
That's fine. A slight elevation is not a problem. It means the rest of the voltage is useful to the motor to spin it up.
I grounded the + from my meter to a screw on the truck and I got the voltage on the ground wire but I didn't seem to get any voltage when grounding to sheet metal I had in the garage.
Well, sheet metal outside the vehicle wasn't what I had in mind for that test. It's not connected to the vehicle's sheet metal because of the rubber tires and non-conductive floor it's sitting on.
The plug that goes to the blower motor is getting volts and adjusts volts as I increase and decrease the the speed on my hvac unit.
Excellent
I don't know how I can test the blower motor wires when the blower fan is pluged into the motor to read the volts when the fan turns on or when it won't turn on...
If you can't poke the meter leads into the backside of the connector, then use the pin trick. Get a couple of pins or safety pins and poke them through the insulation of the wires you want to check out. Place the meter leads on the pins. When you're done, the insulation will heal itself when you remove the pins.
Also, when I put my head near the blower motor and disconnect the input ground wire from the car to the module and quickly tap them together, I hear a clicking sound that seems to be coming from the blower motor. About 1 out of 5 times the blower motor turns on.
Sounds like bad blower motor brushes or a dead mouse in the plenum. Drop the motor and test it on your bench with 12V.
 

dgreen

Original poster
Member
Jan 22, 2012
6
I think you may be correct about the blower motor. Here is what i found from another website.

Here is a new development in this repair. It seems that General Motors has added or changed a circuit in the new module that reduces what they refer to as "Thermal Events". In doing so the new module does not always play well with aged blower motors. What we wind up with is this. The blower motor will not work on an engine restart unless the a/c controls were switched off before the ignition was cycled off and back on after the engine is running again. The two immediate ways to address this issue is to learn to remember to cycle the switches in the above manner or replace the aged blower motor with a new one. I suspect there may be a software update somewhere down the road but that will require dealer level programming abilities. Since the replacement part is only available from GM or throughan AC Delco distributor we are all being subjected to this problem.

So I tried the above cycling method and it worked properly. I had my buddy pick up a blower to see if that corrects the problem. I may call a dealer tomarrow to see if they can offer a software update cheaper than the $90 part from AutoZone.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
dgreen said:
... I may call a dealer tomarrow to see if they can offer a software update cheaper than the $90 part from AutoZone.
Bill Gates is a greedy SOB, but he's forced to give his updates away for mostly free. GM is still partially owned by us taxpayers, and they NEVER give away updates for as little as $90. :hissyfit:

Good find on that explanation.
 

racsan

Member
Feb 5, 2012
15
im working on a co-workers vehicle, its a '04 trailblazer, 4.2 6, auto temp controls, blower stays running, determined its the module, cant seem to find it anywhere. dealer only part? the picture above looks like it shows both the digital controler and the resistor version for the manual climate control setup. the resistor version is available locally at parts stores, the square 3 pin "black box" isnt even listed. is there really some way to use the resisitor box for the auto climate setup? i defintly want to make sure im going after the right part, its one thing to goof on your own stuff, dont want to be wrong when its not my vehicle (or money) involved. cant even find a definite price for the digital module, im guessing its around $100. bad time of year for a blower motor to not be working right. in addition, the battery was unhooked to prevent overnight drainage, now it idles too slow (about 500 rpm) and runs a little rough. i read somewhere it may have a dirty throttle body & the computer has to "re-learn" how to control things.
 

The_Roadie

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Nov 19, 2011
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racsan said:
im working on a co-workers vehicle, its a '04 trailblazer, 4.2 6, auto temp controls, blower stays running, determined its the module, cant seem to find it anywhere.
Many aftermarket stores have them. What ones have you checked? Try their on-line sites to make sure you just aren't getting an incompetent clerk. Check rockauto also for possible alternate part numbers.
dealer only part?
No. At the dealer, list price is $130+ IIRC.
the picture above looks like it shows both the digital controler and the resistor version for the manual climate control setup.
Actually, it's a new version of the digital one. The resistor pack version is not in that picture. I'll look for a picture that has all possible versions in it. Check this thread: http://gmtnation.com/f23/04-envoy-blower-motor-blower-module-problems-277/
the resistor version is available locally at parts stores, the square 3 pin "black box" isnt even listed. is there really some way to use the resisitor box for the auto climate setup?
Not without fixing it to one speed only. If all you want is one speed for now, high, a jumper wire can accomplish that.
i defintly want to make sure im going after the right part, its one thing to goof on your own stuff, dont want to be wrong when its not my vehicle (or money) involved. cant even find a definite price for the digital module, im guessing its around $100. bad time of year for a blower motor to not be working right.
If you pull the correct fan fuse, you won't have to disconnect the battery. Underhood fuse #35
in addition, the battery was unhooked to prevent overnight drainage, now it idles too slow (about 500 rpm) and runs a little rough. i read somewhere it may have a dirty throttle body & the computer has to "re-learn" how to control things.
Got it in one. Dirty throttle body. $5 fix, plus the time to remove it from the vehicle because it's the BACK side of the plate that needs cleaning.
 

racsan

Member
Feb 5, 2012
15
i found the fuse to pull today when i got to look at the truck, i was told the truck had a issue last night but was unable to go check it out right away. places i check were autozone & advance auto. i looked online at o'reilys & napa, it looked like the correct part on the napa site, but you couldnt rotate the picture to see the plugin. i know the clerk at advance auto was a overwhemed kid who was unbelieveably stressed out for some reason, they had a $100 part on the computer screen listing but didnt have it in stock. the computer at autozone only showed 1 part, it was the part meant for the manual fan control, had the long 7 pin plugin, no mention of the auto temp setup, maybe its unusual to have the higher end part in the chevy chassis, shoulda had a lookup done on a gmc envoy where auto temp control may be the only system there is for that chassis. not that it really comes into play, but i thought id mention that this truck has 106,000 miles on it. thanks for repliing, my usual blazer forum i visit doesnt have much information on the trailblazer chassis, and this one is the first one ive ever worked on, in the past 5 months ive put on brakes, tie rod ends, water pump and now this issue. on edit: what exactly do i call this part when i go looking, "fan speed control module" ? some of the counter people you deal with would (try) to look up a spark plug for a diesel and bring something back to the register for you to buy, having the correct name of the part might be helpfull, since the part for the manual heat-a/c is similar looking and goes in the same spot.
 

dgreen

Original poster
Member
Jan 22, 2012
6
racsan said:
i found the fuse to pull today when i got to look at the truck, i was told the truck had a issue last night but was unable to go check it out right away. places i check were autozone & advance auto. i looked online at o'reilys & napa, it looked like the correct part on the napa site, but you couldnt rotate the picture to see the plugin. i know the clerk at advance auto was a overwhemed kid who was unbelieveably stressed out for some reason, they had a $100 part on the computer screen listing but didnt have it in stock. the computer at autozone only showed 1 part, it was the part meant for the manual fan control, had the long 7 pin plugin, no mention of the auto temp setup, maybe its unusual to have the higher end part in the chevy chassis, shoulda had a lookup done on a gmc envoy where auto temp control may be the only system there is for that chassis. not that it really comes into play, but i thought id mention that this truck has 106,000 miles on it. thanks for repliing, my usual blazer forum i visit doesnt have much information on the trailblazer chassis, and this one is the first one ive ever worked on, in the past 5 months ive put on brakes, tie rod ends, water pump and now this issue. on edit: what exactly do i call this part when i go looking, "fan speed control module" ? some of the counter people you deal with would (try) to look up a spark plug for a diesel and bring something back to the register for you to buy, having the correct name of the part might be helpfull, since the part for the manual heat-a/c is similar looking and goes in the same spot.

Autozone didnt have the correct part when I searched, it was for the "Manual" HVAC system only. I bought mine at O'Reilly's. GM no longer makes the 3 Pin Connector so you may have to do some minor wiring, I simply used the the Heat Shrink wire connectors. If the unit doesn't work correctly you might have to buy a blower motor as well, that fixed my problem.
 

racsan

Member
Feb 5, 2012
15
she stopped by a gm stealership today and got the module, was $107, 6 bucks for a can of throttle body cleaner spray. new module has no plug-in socket for the 3 wires coming from the dash controls, has one long plug. the harness that plugs into the module has the plug with wires that goes into the fan motor and the 3 remaining wires you just spice together with the original wires after sniping off the old small square plug. works fine now. cleaned the throttle body up, its puzzling how something after the air cleaner element can get so dirty.
 

The_Roadie

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Nov 19, 2011
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Portland, OR
racsan said:
she stopped by a gm stealership today and got the module, was $107,
$107 at the dealer!?!?! :eek: Shockingly CHEAP. Thanks for the news we can share with other victims. What part number are they selling?
its puzzling how something after the air cleaner element can get so dirty.
Not puzzling at all when you hear that GM saved a dime per I6 engine by omitting what every other engine uses to prevent that - a PCV valve. :hissyfit:
 

racsan

Member
Feb 5, 2012
15
gosh, i dont know what part # was on the box, left all that in her truck when i left it last night. didnt notice at the time that there was no pcv valve, but now that youve mentioned it, i do recall just a hose from the valve cover to the air silencer box, figured it drew air at that spot, but i guess thats just the crankcase vent to the intake. its the only 4.2 ive ever seen, and im very unfamiler with it. not sure that id ever own one myself. seems like g.m. likes to do dumb things like use tie rod end ball joints that arent heavy enough for the vehicle that their on, have no grease fittings and they wear out rather quickly, $50 per side for the "cheap" ones. i think the ball joints on the S-series blazers are too small for the vehicle as well, door hinge pins that arent heavy enough for the doors they hinge upon. sure theres some good things about the platform, im just picky & see where they could have made it better. i dont understand going to 6 lug wheels, but use undersized suspention parts. im not a big fan of the newer ford products either. never been a dodge fan. and imports? not really done much with 'em aside from brake jobs & oil changes. someday i'll probly end up with something newer, but for the time being, i'll just keep my old junk on the road ('93 ranger, '97 S-blazer) and work on everyone elses newer stuff-and take notes!
 

racsan

Member
Feb 5, 2012
15
well 2 days later i hear the blower aint working at all, time to go do voltage checks & possibly replace the blower motor. they sure dont make things like they used to. on edit, a few hours later: well, im confused. i checked for voltage and it was there, seemed to have a good ground at the motor plug hook-up. i suspected maybe a bad fan, so i pulled it out and took it to the front of the vehicle , hooked up some jumper wires and wow! no motor issue here, the torque of the motor bout took it from my hands! i thought maybe theres insuffiecent ground, maybe i need to run a ground from the underdash sheetmetal to the orange wire going directly to the fan (since the purple lead is the + hot wire) put things back together and tryed it just for the heck of it. working! thought maybe i just had a bad motor/plug connection. put glove box & lower dash panel back on. played with the settings a bit, turned vehicle on 7 off. as far as i could tell it was good to go. but then about a hour ago i get a text saying its not working...again. could anything else be bad here? im about going to have to rig a light up to the motor wires to see if there is indeed voltage loss when motor doesnt work. im sure the motor doesnt have a dead spot in it, i tryed it more than once jumpering it, it took off every time. might have to rig a toggle switch up, sure it would be high or nothing, but high only is better than nothing.
 

neelskit

Member
Dec 7, 2011
69
Check the resistance from the ground on the fan plug to chassis ground with a DMM. It could very well be a bad fan even though you've "jumped" it several times. IIRC, a bad fan is what causes the module to fail- excessive current draw cooks it to death.
 

dgreen

Original poster
Member
Jan 22, 2012
6
racsan said:
well 2 days later i hear the blower aint working at all, time to go do voltage checks & possibly replace the blower motor. they sure dont make things like they used to. on edit, a few hours later: well, im confused. i checked for voltage and it was there, seemed to have a good ground at the motor plug hook-up. i suspected maybe a bad fan, so i pulled it out and took it to the front of the vehicle , hooked up some jumper wires and wow! no motor issue here, the torque of the motor bout took it from my hands! i thought maybe theres insuffiecent ground, maybe i need to run a ground from the underdash sheetmetal to the orange wire going directly to the fan (since the purple lead is the + hot wire) put things back together and tryed it just for the heck of it. working! thought maybe i just had a bad motor/plug connection. put glove box & lower dash panel back on. played with the settings a bit, turned vehicle on 7 off. as far as i could tell it was good to go. but then about a hour ago i get a text saying its not working...again. could anything else be bad here? im about going to have to rig a light up to the motor wires to see if there is indeed voltage loss when motor doesnt work. im sure the motor doesnt have a dead spot in it, i tryed it more than once jumpering it, it took off every time. might have to rig a toggle switch up, sure it would be high or nothing, but high only is better than nothing.

Try the sequence below. If it works then you need to replace the blower motor. You can easily buy the blower motor from your local parts store and plug the wire in from the control module while holding the fan in your hand. You can usually return these items if they are "not installed".

Here is a new development in this repair. It seems that General Motors has added or changed a circuit in the new module that reduces what they refer to as "Thermal Events". In doing so the new module does not always play well with aged blower motors. What we wind up with is this. The blower motor will not work on an engine restart unless the a/c controls were switched off before the ignition was cycled off and back on after the engine is running again. The two immediate ways to address this issue is to learn to remember to cycle the switches in the above manner or replace the aged blower motor with a new one. I suspect there may be a software update somewhere down the road but that will require dealer level programming abilities. Since the replacement part is only available from GM or throughan AC Delco distributor we are all being subjected to this problem.

Hope this helps. I had a similar issue and I replaced my control module and also had to replace the blower motor as well.
 

racsan

Member
Feb 5, 2012
15
well, its going once again, i checked everything over, had voltage where it was supposed to, and even though the old motor could be "jumpered", it wouldnt run when plugged in to the module. put a new blower in and no problems, even sounds like its moving more air than the old one was. (but that could just be my imagination) hopefully this cures it, there really cant be anything else. it did look kind of dirty inside the old motor, what i could see through that vent hole that the angled rubber boot fits into. thanks for the help/insights!
 

burnedfingers

Member
Mar 4, 2012
16
New member here 2004 GMC Envoy I-6 auto temp control

Ok, replaced the blower control unit last fall with a new one from GM (newer version). Checked current draw on the blower motor -ok. Re-installed the blower motor and the control module. Blower works some of the time. Digital outside temp reading didn't work above 50degrees and now doesn't work at all. Stuck on 50 degrees. Sometimes blower will work by turning it down about half way and then starting it. from what I have read it might sound like a ground #201 problem or possibly a bad head unit.

How do I access ground 201? What is a new auto temp control head going to cost? PN?

Thanks in advance
:smile:
 

burnedfingers

Member
Mar 4, 2012
16
Had saved the old control unit. Dissassembled it to remove the bad Fet. The heatsink compound is in really bad shape dried out thus helping with the demise of the semiconductor. Anyway its pretty easy to remove with a desoldering station. Looking at it under a glass the PN is IRFBA1405P couldn't see the 1 on it without a little magnification.
 

The_Roadie

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Nov 19, 2011
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burnedfingers said:
... the PN is IRFBA1405P ...
Currently available parts that will drop right in are IRF1404LPBF (available from Mouser, Newark, Digikey and a raft of other places) for under $5 plus a bit of shipping) and IRFBA1405PPBF a slightly more robust device for $6 + shipping.

To locate parts like this quickly at work I use FindChips.com Online Electronic Component Distributor Inventory Search. One of the test systems I'm product manager for is designed to test all the parameters of these exact FET devices.
 

burnedfingers

Member
Mar 4, 2012
16
Thanks for the reply. I had no problem finding the Fet on Mouser for $5.69 plus shipping. Just added it to my already started weekly order. Any ideas on the #201 ground?
 

burnedfingers

Member
Mar 4, 2012
16
Quote:
bad fan is what causes the module to fail- excessive current draw cooks it to death.


That is one of the causes. Another is the very poor design as the FET does not contact the heatsink correctly to cool.
 

RayVoy

Member
Nov 20, 2011
939
burnedfingers said:
Quote:
bad fan is what causes the module to fail- excessive current draw cooks it to death.
Actually, I don't believe this statement, yes, a "bad" fan that is drawing excessive current will burn out the speed control module; however, these modules fail way more often than the fan motor fails. I believe it was a penny-pinching, poor design.

burnedfingers said:
Quote:
That is one of the causes. Another is the very poor design as the FET does not contact the heatsink correctly to cool.
This may be so........... I've not had the module apart to see if this is a common design problem.
 

The_Roadie

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Nov 19, 2011
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RayVoy said:
Actually, I don't believe this statement, yes, a "bad" fan that is drawing excessive current will burn out the speed control module;
I was reading about this more as the vehicles age. In the old times, fan bearings would deteriorate and the fan would get slower and slower and then stop and never burn out the fuse. Nowadays, the resistor pack or the speed control module burn out from current more than they were characterized with. Engineers failed to do the math of what happens as the fan ages. The failure mechanisms are evolving as the population of trucks ages. One of my specialties at work is to deal with oxidized connectors, overheated wiring, filters, and fans as my systems get older and maintenance sometimes is neglected.
 

burnedfingers

Member
Mar 4, 2012
16
You are correct in that the motor condition can and does raise hell with the controller. The design of the controller in my opinion is faulty. The FET is not fastened down to the heatsink but is supposed to come in contact with it. If we know semiconductors we know that they need to be heat sinked properly for heat transfer to happen. If not then they simply cook until they no longer function or they short out. I will try to insert an image or two of the internals of the blower control assy.View attachment 19943

There is a screw that holds the case together but nothing to apply pressure to sink the FET to the heatsink. Note* FET has been removed for replacement procedure. As the picture shows the heat sink compound is not mashed thin as it would be if there were proper pressure applied to it. The thickness of the heatsink compound is .050-.060 and it should be less than 1/2 of that to be effective.
 

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RayVoy

Member
Nov 20, 2011
939
the roadie said:
I was reading about this more as the vehicles age. In the old times, fan bearings would deteriorate and the fan would get slower and slower and then stop and never burn out the fuse. Nowadays, the resistor pack or the speed control module burn out from current more than they were characterized with. Engineers failed to do the math of what happens as the fan ages. The failure mechanisms are evolving as the population of trucks ages. One of my specialties at work is to deal with oxidized connectors, overheated wiring, filters, and fans as my systems get older and maintenance sometimes is neglected.
I agree, as the vehicle (or any electronics) age, oxidization of connectors becomes a problem. However, these connectors are external to the blower motor, that is the point I was trying to make. The fan is probably good, the problem is in the connectors and in the control module.

Just an aside, with the environmental conditions we live with, oxidization is a problem everywhere. In Saint John, we have 2 pulp/paper mills, one west of downtown, the other is east of downtown.

The emissions are regulated, however oxidization is considerably higher here than other parts of the province.
 

Stamper75

Member
Mar 28, 2012
1
I have an 05 Trailblazer with the automatic temp controls and my fan wouldn't turn off even with the key off like some of you all. I pulled the #35 fuse and it quit. I took out the old control module and it was pretty badly corroded. I got the new GM version where you have to splice the wires and installed it. It works once in awhile like some of you guys. I tried to turn the heater off and then turn the engine off like some people have suggested and it didn't work. It works when it wants to. All my wires seem fine and the ground seems in place. Any other ideas??
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
Stamper75 said:
Any other ideas??
Flaky module, connectors, or splices. Did you solder the splices :thumbsup: or use butt crimps :no: ? Can you inspect the 2-pin connector going to the blower motor carefully? Do you have a meter and know how to use the "push a needle through the insulation" trick to check voltages on wires that are still connected?

I don't know of any reason the order of turning things on and off makes a bit of difference in this system. :confused:
 

bruhaba

Member
Apr 17, 2012
118
the roadie said:
Currently available parts that will drop right in are IRF1404LPBF (available from Mouser, Newark, Digikey and a raft of other places) for under $5 plus a bit of shipping) and IRFBA1405PPBF a slightly more robust device for $6 + shipping.

To locate parts like this quickly at work I use FindChips.com Online Electronic Component Distributor Inventory Search. One of the test systems I'm product manager for is designed to test all the parameters of these exact FET devices.

Thanks Roadie! The controller in my 2005 Tahoe shorted out and the blower would not shut off. Pretty obvious that the FET had failed. I first bought a new module and after having intermittent trouble with the updated blower motor controller I installed as a fix, I refused to replace what I think is a good blower motor as well just because the "updated module" doesn't run an old blower consistently, I returned the new "updated" controller and replaced the mosfet in the old one I had using the part Roadie suggested. IRFBA1405PPBF

It was really an easy job to de-solder and re-install the new one. So far it's working well. 10 bucks is much better than replacing my 130 dollar blower motor and 100 dollar control unit.

Thanks again!
 

satcat

Member
Dec 10, 2012
2
the roadie said:
Currently available parts that will drop right in are IRF1404LPBF (available from Mouser, Newark, Digikey and a raft of other places) for under $5 plus a bit of shipping) and IRFBA1405PPBF a slightly more robust device for $6 + shipping.

To locate parts like this quickly at work I use FindChips.com Online Electronic Component Distributor Inventory Search. One of the test systems I'm product manager for is designed to test all the parameters of these exact FET devices.

What heat sink compound would you recommend, can I just use Arctic silver...I bought the "new" module [ GM 89019351 = AC 15-81728] five months ago,and do not want to buy the "newer" one.
Would the new FET ,with new compound last any longer than the original..
 

satcat

Member
Dec 10, 2012
2
the roadie said:
Arctic Silver is a fine compound. I wouldn't change a component unless it's failed, though.

Thanks for the reply.. I was referring to " bruhaba" who just used his original failed module, and replaced the faulty "IRF1404LPBF" mosfet. Would this work for a long time, or would it eventually fail like the original mosfet. Keep in mind new and better thermal compound.I would rather spend 5 dollars, Than another 80 or 90$ on the second or third update to this module...
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
I would spend $5 a year rather than $50 once. Nobody can ever tell when a component will fail, unless the original heat sink job was faulty and the device overheated, and your replacement is installed with more care and will stay cooler.
 

Bruce G

Member
Dec 15, 2012
1
Wish I had found this post earlier. Replaced both motor and module just to have same problem sure did hurt the pocketbook. Would have preferred to change the chipset rather than cutting up the old harness for new connector. Don't know why but shutting off fan before killing engine does work. On a positive side the new fan motor by Delco allows you to throw away the plastic motor cover/ moisture collector on the Envoy.
 

Jetfxrz

Member
Oct 17, 2013
1
the roadie said:
Currently available parts that will drop right in are IRF1404LPBF (available from Mouser, Newark, Digikey and a raft of other places) for under $5 plus a bit of shipping) and IRFBA1405PPBF a slightly more robust device for $6 + shipping.

To locate parts like this quickly at work I use FindChips.com Online Electronic Component Distributor Inventory Search. One of the test systems I'm product manager for is designed to test all the parameters of these exact FET devices.

A friend has a 2007 Tahoe, the battery went dead. She had been complaining of the fan blower not working well enough to defrost the windows and seemed to be stuck on low. She has the automatic climate control, and regardless of the fan speed selection (Auto or Manual) the fan just barely pushed any air. I checked power at the fan and found 11.9 volts regardless of fan speed selection when checking from connector(purple wire) to a good ground. Checking the connector from Purple to Black, I only got 3.4 volts. The connector was really dirty by the way and required some cleaning just to get a good read on it.

I've decided to replace the FET in the control module. Ordered from Digikey per your instructions above, that was a snap. In the meantime (until the part arrives) I snipped the black ground wire between the connector and the module (to keep the fan from running all the time) and installed a SPST toggle from ground to the black wire connection point. This provides a full ground for the blower motor and now it can blow on high speed to clear her windshield. Having high blower speed selection via a toggle switch is much better than windows that fog up while driving. I'll post back my results when the part is received and installed. I just wanted to post my emergency fix in case anyone else is stuck in a similar situation.
 

billzie

Member
Aug 20, 2012
86
Athens, OH
Thanks for this thread and site in general. I've been having similar issues with my '03 LT EXT, blower works as it should only occasionally, must remove fuse to ensure no draw, etc.
My questions/concerns:
I'm poor so DIY and low cost are key. I'm willing to try replacing the MOSFET if I'm capable, anyone have a DIY on this? I'm mechanically better than inclined, but electronics aren't my strong suit. Is the 405 MOSFET (IRFBA1405PPBF) preferable over the 404 unit? What can I use as the heatsink goop that a typical garage mechanic like me might have on the shelf, dielectric grease? Any other issues I need to be aware of or should take care of while doing this repair? Oh, I live in a small rural town so not a lot of access to a lot of DIY type shops and all the typical chain stores here are mini compared to city stores.
Thanks for all your help, Bill.
 

bruhaba

Member
Apr 17, 2012
118
Been using the fix without problems. Don't overt think it. Get some heat sink compound, the MOSFET, some desolder wick, put the new one in and be done with it. Big thanks to roadie for the FET recommendation.

I have electronics experience and it ws cake, but as long as you know how to solder you should be fine.
 

billzie

Member
Aug 20, 2012
86
Athens, OH
Ok, we have a radio shack but its small like they've become over the years but this one doesn't carry a whole lot of DIY stuff. I'm just trying to keep my out of pocket as minimal as possible. I've soldered wires before but never on a board. I've never used des older wick but just seeing the name gives me an idea of how it works. Is there a frontwards/backwards way to put in the MOSFET? And is that 405 the prefered mosfet? Sorry about any over thinking, it's what I do lol.
Too bad someone here didn't order a few handfuls of these and pass along savings to us lol. If I had the extra $ I could see offering these for $5-6 shipped which would be a savings for the buyer and a small profit for selle lol.
Maybe I'll cash in my Christmas coal and do it.
More importantly my knee needs to heal a bit more since surgery before I'm doing any work on the TB.
Bill.
 

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