NO FAN!!!

bigytwotone

Original poster
Member
Dec 7, 2011
489
Dawson creek BC Canada
Ok so i have a 2003 trailblazer LTZ 4x4 with 124,000km's it is -16c here and last night my heater fan was working. then i lent my truck to off road bella and this morning the fan wont come on. The truck was left outside and not plugged in. the fan wont come on when the truck is running and it wont come on when i turn the key to run with out starting it so i looked at all the fuses and there all good and i have read about both speed sensors and bad connections what do i do so she has the truck at work right now so i cant do much. but when she gets here what should i do??
 

The_Roadie

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Nov 19, 2011
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Do you have the automatic/digital control system or the 5-speed manual system?

The blower motor might have a bad bearing and need a bit of warmth to get going,
or the connector on the speed control module or resistor pack could be damaged from overheating,
or the module or resistor pack could be dead.

Or a fuse could be bad and just looking at them isn't always sufficient.

Do you have a meter and know how to use it?

Can you take the blower motor out and test it on a bench?

It's not easy to get to, but it's sort of obvious where it is behind the glove box.
 

bigytwotone

Original poster
Member
Dec 7, 2011
489
Dawson creek BC Canada
the roadie said:
Do you have the automatic/digital control system or the 5-speed manual system?

The blower motor might have a bad bearing and need a bit of warmth to get going,
or the connector on the speed control module or resistor pack could be damaged from overheating,
or the module or resistor pack could be dead.

Or a fuse could be bad and just looking at them isn't always sufficient.

Do you have a meter and know how to use it?

Can you take the blower motor out and test it on a bench?

It's not easy to get to, but it's sort of obvious where it is behind the glove box.

i have the automatic/digital control system i have tested the fuses with my meter. i do have a meter and i do know how to use it :biggrin::cool:
at the moment i can't take the blower out right now but maybe tonight. when i test the blower what do i do do i hook 12v to it?? and how do i tell what pegs are for power???(pegs where the plug plug's into) i have never done that.
 

STLtrailbSS

Member
Dec 4, 2011
1,617
Im going to but in to help out

Your blower motor only has two wire simple red and black it has a connection down by the resistor. I had the same problem a couple of months ago I'm borderline guaranteeing your blower speed control module is fried you can tell the minute you pull the harness connection the pins will be fried literally... definitely take a look at that before pulling the motor. If it is the blower speed control module you will have to buy the blower speed control module itself and a pig tail connector which you have to cut the existing pin connector and match up the wires with a crimp connection or solider, all in that nice small footwell space. PITA lol


This message has been edited to meet standards of the roadie :biggrin:
 

The_Roadie

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bigytwotone

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Dec 7, 2011
489
Dawson creek BC Canada
ok guys how do i go about testing the blower speed control module i took everything apart and everything looks good none of the conectors are burnt or broken. is there any way of getting this thing to work with out this speed control module??? any help would be awesome
 

The_Roadie

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You can only test it if you have a bench with a 12V supply and some load resistors. It might be the FET inside, in which case the OS had a tutorial on changing the transistor. As long as you know it has power going to the module (did you check fuse #35 - it's an odd J-case unit), then the RED wire at the module should have power. Just jump that to the purple wire on the motor with a switch, and at least you will have the blower while you buy a new module. Note it will run even with the ignition off unless you turn off the switch.
 

bigytwotone

Original poster
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Dec 7, 2011
489
Dawson creek BC Canada
ok so i went to Napa and almost SH#$ MY PANTS the blower speed control module is $218 i will be putting a switch till i can afford that and a new blower. is there any way to free up the blower it is starting to get stiff to turn i can't find a oiling port on the motor i can get the motor rebuilt but if it just need oil i don't what to spend money if i don't have to. i work with these motors all the time so rebuilding these is not an issue.

Thankyou: The Roadie your a big help
 

The_Roadie

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Nov 19, 2011
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Sorry, forgot you were in Canada. Never had a problem with mine, so I don't know about oiling. Here, blower motors are under $100, and modules are $80 or so on Ebay and many other places:

[EBAY]360424784786[/EBAY]
 

bigytwotone

Original poster
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Dec 7, 2011
489
Dawson creek BC Canada
See you are awesome i almost die and you show me new light and help me get back to having a working truck. now when i put in the switch i need to ground it?? and will the fan be on full blast?? i had my meter out and tested. I have 8.0v at the blower when i turn on the heat and 12.4 v on the controler side of the speed module dose that sound right with the speed module being dead?? and i should be getting 12v at the blower right??
 

The_Roadie

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Nov 19, 2011
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You should have close to 12V at the blower if you manually hit the UP-SPEED button to force it. Sounds like your module isn't dead but just the motor is drawing too much current and isn't moving because of the dry bearing or a dead mouse inside the housing.

Grounding the switch? No. I've posted the schematic before in other threads, I think, but all you want the switch to do is connect the module's input, the RED wire that should always have 12V on it, to the PURPLE wire going to the motor. The motor is already grounded by its black wire. Putting ground anywhere on your SPST switch is going to blow a fuse.

But abandon the switch idea for now. You have a bad motor.
 

bigytwotone

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Dec 7, 2011
489
Dawson creek BC Canada
Ok I think i miss worded my last state meant when i unplugged my blower form the module and tested for power i only get 8.v coming from the speed module so im not to sure if the motor is totally at fault.
 

The_Roadie

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8V with the motor unplugged is possibly good. What it means is that the speed control module isn't on the highest speed. Giving less than 12V is how the module adjusts the speed.

What you need to do to troubleshoot the system is plug them back together, and see what voltage the module sends to the motor. If it's low, then the motor could be locked or the module could be damaged. Then, as I recommended, remove the motor and put 12V right on it and see if it spins.
 

bigytwotone

Original poster
Member
Dec 7, 2011
489
Dawson creek BC Canada
Ok so i tested the voltage so here's what i got i had the fan cranked up and only got 7.1v at the motor and with the motor disconnected
View attachment 18071
So the voltage dose not change if the blowers connected or if its not connected it is always 7.1v
i have not bench tested the blower yet I have to go grocery shopping when i get home i will test it.
 

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bigytwotone

Original poster
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Dec 7, 2011
489
Dawson creek BC Canada
Ok I bench tested the blower motor and it did not work at all I tryed every thing so since its dead I decided to dig in to it I took it right appart and tryed to jump out the dead winding that I found and it worked. But it spun fo like 30seconds then stoped and I saw smoke well I welded the winding together opps well had fun anyways so I ordered the new one should I. Get a new speed module???
 

The_Roadie

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The bad motor could have damaged the speed control module. Can't tell for sure until you hook them together. At least with a good motor you can do the switch trick we first started discussing and get some heat going while you wait for the module if you need one.
 

The_Roadie

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Nov 19, 2011
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A bad speed control cannot hurt the motor. All it can do is provide 12V even if the key is off, or too low a voltage. Neither one is damaging. Just annoying. Good question to worry about, though. I like cautious owners.
 

bigytwotone

Original poster
Member
Dec 7, 2011
489
Dawson creek BC Canada
Awesome the roadie I dont know when but I am going to drive down in your direction we should meat one day blower should be here on monday im excited now. Now when and if I do the switch deal will thefan de on high all the time?? Or will I be able to change the speed?
 

neelskit

Member
Dec 7, 2011
69
bigytwotone said:
Ok I bench tested the blower motor and it did not work at all I tryed every thing so since its dead I decided to dig in to it I took it right appart and tryed to jump out the dead winding that I found and it worked. But it spun fo like 30seconds then stoped and I saw smoke well I welded the winding together opps well had fun anyways so I ordered the new one should I. Get a new speed module???

If you can solder, you can save some money by replacing the HFET in the module that has most likely failed. Here is the part:

Digi-Key - IRF1405LPBF-ND (Manufacturer - IRF1405LPBF)

You may have to modify the pins for it to fit on the PCB correctly.
 

bigytwotone

Original poster
Member
Dec 7, 2011
489
Dawson creek BC Canada
ok so i got my new blower and geuss what no worky i tested it and still no go so what am i doing wrong i though oh the roadie told me about a switch trick i tryed that and still no go and all of my fuses are good i even tried changing them but still no go what is wrong with this thing?? i need help
 

bigytwotone

Original poster
Member
Dec 7, 2011
489
Dawson creek BC Canada
IF i were to cut the black wire that gose from the speed control to the fan and ground that would that work???? be like on its own ground till it warms up and i can get a chance to look at all the grounds??
 

The_Roadie

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Nov 19, 2011
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Portland, OR
I don't have access to my shop manuals right now. But there are only two wires going to the motor. What else could it POSSIBLY be?

Trace the black wire from the motor. If it disappears into a harness, you've lost it. If it goes to a nearby screw to some sheet metal, you win. Inspect it. You can install your own bypass wire safely. Splice in to the black wire at the motor, and put your OWN screw into nearby sheet metal. Use a ring lug at the sheet metal end of the wire unless you want to go redneck.

View attachment 18172
 

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bigytwotone

Original poster
Member
Dec 7, 2011
489
Dawson creek BC Canada
ok so the black wire to the fan has no volts so i cut it and hooked it to ground and it works now my truck is running and that fan is going and worming the truck up YES!!!! so i have to check my grounds this summer but i think i am going to replace the speed control because it looks like crap andi think that is the problem well im going t go i have arenas to do and i now have heat and can do them. thanks roadie for the help and i will be picking your brain when it worms up. thanks again everyone.
 

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