Resistor pack

[Ghost]

So I replaced my hvac control module but still not working on air settings 1,2,3. So now I know it is this:

The part has soo many part#s I have found a few but need to know of this one will work:

http://www.ebay.com/itm/RU377X-HVAC-Blower-Motor-Resistor-/261086633006

I ordered an generic part @ Orielys autoparts but its $15 more than this guy on eBay and it.looks to be the same part. I Havent payed for the order on orielys yet...you don't till you pick it up. The cheapest ac delco.I could find was $39.95

 

[The_Roadie]

Should be fine, but any local aftermarket parts store should have an equivalent for around $30. For me, local convenience is worth the $15. YMMV.

 

[mrphoenix80]

Make sure the connector terminals are not burned. It is a common problem on these trucks.

 

[Ghost]

Make sure the connector terminals are not burned. It is a common problem on these trucks.

Yea all the connections look new with no burnt parts. But the resistor card looks fried. I tried to fix but still air speed settings: 1,2,3 don't work. All will be great once the part gets here.

 

[CaptainXL]

Yea all the connections look new with no burnt parts.

And the connector may look fine until closer inspection. Many people ended up buying the connector to fix it completely. Including yours truly.

GM technical service bulletin says to replace both resistor and connector harness in order to properly fix this. And for good reason. As the connector appears to be the main source of the problem..

http://www.amazon.com/gp/product/B0040CVQO8/?tag=gmtnation-20

View attachment 28046

 

[tmm217]

So what is the cause of this melting? I'm now on my second melted pack. What can be done to stop this from constantly happening? I did replace harness with a harness from a junk yard. Is that my problem?

 

[CaptainXL]

I did replace harness with a harness from a junk yard. Is that my problem?

Yes, that's the problem. Any vehicle within a certain amount of mileage would start to show signs of harness failure. Just get the one I referenced and you should be good to go. It's not rocket science to replace. And it's cheap insurance.

The cause is undoubtedly high resistance at the connection which causes heat and the plastic coating of the wire to melt. The plastic wicks into the connector/charring and thus causing intermittent or no continuity.

 

[AtlWrk]

So what is the cause of this melting?

Poor design exacerbated by time, use, heat, corrosion, vibration, etc.
I can't speak to the actual current drawn by the blower motor but it is fused at 40 amps for setting 5 (30amps for lower settings). Delphi rates the connector at 30amps max under ideal conditions so...

I'm now on my second melted pack. What can be done to stop this from constantly happening? I did replace harness with a harness from a junk yard. Is that my problem?

New terminals and a new resistor pack are the best defense in lieu of a better designed connection IMHO.

 

[The_Roadie]

I can't speak to the actual current drawn by the blower motor ...

I really have to get into mine and measure it so we all know. My conclusion is that the resistor pack AND the harness connector are undersized for the application, since they fail in MANY, MANY GM vehicles. That means the aftermarket companies see a market that they fill for cheaper than GM.

HOWEVER, an aging blower motor with deteriorating bearings will draw more current as it gets older or on cold starts, and THAT phenomenon explains how some owners replace the resistor pack and/or the harness connector, and the subsequent ones fail faster than expected. Those folks (I believe) have a deteriorating blower motor and would benefit from swapping it out, even if their fuses aren't blowing.

 

[CaptainXL]

That's good Bill. According to Wells the cause is from too much amperage which corroborates your hypothesis. Guess I should check my motors amperage draw as well.


[video=youtube;B4zGM6zE6Tg]http://www.youtube.com/watch?v=B4zGM6zE6Tg[/video]

 

[tmm217]

Thanks Captain. That video hit it on the spot. I should've checked the amperage in the first place. Guess I just band aided the problem. So it seems that what happens is the motor over draws amps then tries to blame it on the resistor pack and harness. It's kinda a hidden problem unless looked at closely.

 

[CaptainXL]

Well Bill brought it up. I just went with what he said and investigated because his reasoning was sound. We both took electronics in college but he is the pro. Kudos to him.

 

[The_Roadie]

Most people don't have the tools (Hall effect sensor or low milliohm shunt resistor plus an oscilloscope with differential inputs) to measure the peak start-up current draw on a motor as it starts up, and even the steady-state current if it's above the 10A limit for most consumer meters. So it's almost a moot point for most truck owners. Replace the resistor pack and the harness connector. If it fails again in a year, replace the motor. Profit.

 

[CaptainXL]

I want the clamp on meter he is using in the video. Seems to handle 20+ amps. It's probably $$$ though.

I was also thinking of getting a pico scope to use as an oscilloscope with clamp on meter. But those are $$$ as well. Ahh well.

 

[Ghost]

I want the clamp on meter he is using in the video. Seems to handle 20+ amps. It's probably $$$ though.

I was also thinking of getting a pico scope to use as an oscilloscope with clamp on meter. But those are $$$ as well. Ahh well.

Probably $2000.00
I have Scopes and lots of tools, thing is I'm lazy LOL! I would rather sit in my behind and chase DX or VHF P25 comms than play mechanic. Maybe once it gets a little nicer here outside I'll drop the mic and work on the TB (the right way).

 

[CaptainXL]

A 2 channel automotive Pico scope is $800. And a 600 DCA clamp is $163. Mind you this is MSRP so should be cheaper. Anyway the clamp meters from Fluke would be cheaper at around $300.

 

[The_Roadie]

I didn't look closely at the video until now. A Fluke 337, eh? Very nice. I have a Fluke Y8100 unit that needs a meter to display the reading. Wouldn't be without it. Actually, I got a spare on Ebay a few years ago and the buddy I bought it for said he'd rather just borrow mine the few times he needed it. (I usually came WITH the meter and that's what he really wanted access to...). Anybody looking to get a cheaper DC ammeter shoot me a PM. Probably $60 shipped unless 100 people want it.

 

[mrphoenix80]

Damn where were you a couple months ago??? I got a DMM kit from MAC for $600. It has the DMM, a low amp clamp (0-30amp with .01amp resolution), a high amp clamp(up to 1500amps), the normal leads, a temp probe, USB cables , And an IR adaptor for PC data logging.
Oh well my MAC guy is great he even let me do it at $40 a week with no intrest. On a side note I have yet to use it more than to check the voltage of a watch battery. Is that not how it always works!

The restistor connector is so common not only on the "T" trucks, but the Colorado and the "C/K" trucks as well. Heck the C/K's even had it as a recall. Now I suspect that what happens is what a professor termed as "thermal runaway". The high amp draw added to the poor connection = high resistance, and that gives off heat. Then the hotter it gets the more resistance it has, more resistance means more heat and so on.

 

[The_Roadie]

Now I suspect that what happens is what a professor termed as "thermal runaway". The high amp draw added to the poor connection = high resistance, and that gives off heat. Then the hotter it gets the more resistance it has, more resistance means more heat and so on.

Precisely. I guarantee that can happen over a much longer term in the electronic systems I've been designing for quite some time. One of my jobs had me doing tech support on systems as old as 17 years. When I originally designed the power distribution system, my CEO was a cheap SOB and made me use tin-plated Molex connectors where I wanted to use connector pins with a gold flash coating that would have added $50 to the cost of a $250,000 system. The CEO of this start-up was gone in 2 years, and starting 8 years out, the systems started to get flaky in exactly the way I predicted. I hate being right. Now I never use ANY connector that's not gold plated, and I have the clout to not get over-ruled anymore.

Although I *know* I won't be supporting these suckers in another 17 years, it's the right thing to do.

 

[tmm217]

I want the clamp on meter he is using in the video. Seems to handle 20+ amps. It's probably $$$ though.

I was also thinking of getting a pico scope to use as an oscilloscope with clamp on meter. But those are $$$ as well. Ahh well.

Try Harbor Freight for an inexpensive meter with amp clamp. Thats what I have and it works for me.

 

[CaptainXL]

Try Harbor Freight for an inexpensive meter with amp clamp. Thats what I have and it works for me.

Harbor Freight doesnt have DCA clamp meters. They just have a couple ACA meters. What do you use?

 

[The_Roadie]

Try Harbor Freight for an inexpensive meter with amp clamp. Thats what I have and it works for me.

Model number, please. I didn't think they ever offered a clamp-on DC ammeter. The sensor for that typically adds $100 to the cost of a normal meter. Not the typical HF market.

 

[Team Dougherty]

I own this one. Sears.com

 

[tmm217]

Model number, please. I didn't think they ever offered a clamp-on DC ammeter. The sensor for that typically adds $100 to the cost of a normal meter. Not the typical HF market.

Oops sorry it only measures AC current.

 

[RayVoy]

Oops sorry it only measures AC current.

As a clamp on, and single wire at that. It will read DC current, but only in series.

 

[wesman43]

I have a little problem with this. I replaced 3 different resistor packs in a 5 day span because the high speed #5 on the blower just keeps going our, and when I replace the pack again, it works for about a day and a half then stops working again. I check all of the connectors to and from the pack and blower, none are melted

 

[CaptainXL]

Sounds like you need to replace the bower motor because that is what is causing a strain on the circuit. If you watch the video they mention that a motor can still be bad and not blow the fuse.

Also the advice Bill gave is solid:

Replace the resistor pack and the harness connector. If it fails again in a year, replace the motor. Profit.

 

[The_Roadie]

I have a little problem with this. I replaced 3 different resistor packs in a 5 day span because the high speed #5 on the blower just keeps going our, and when I replace the pack again, it works for about a day and a half then stops working again. I check all of the connectors to and from the pack and blower, none are melted

Are you shotgunning the resistor pack without troubleshooting? Have you checked the voltages at the connector with your meter? Could be a problem with front fuse #35 or the relay. Have you replaced the harness side connector in all this?

 

[wesman43]

Are you shotgunning the resistor pack without troubleshooting? Have you checked the voltages at the connector with your meter? Could be a problem with front fuse #35 or the relay. Have you replaced the harness side connector in all this?

No, I haven't replaced the harness or anything. I just wanted to rule out the possibility of shitty manufacturing but such a short timespan, its akward because every other speed except 5 works and its that way every time. Yeah I will have to check the voltage and do some troubleshooting, I mean I really don't use #5 anyways and this was a month or two ago. I'll have to become a midget contortionist to do some troubleshooting

Edit: sorry it actually looked like the person that had it before me switched out the resistor pack because it was an aftermarket one to begin with, so I suspect something with the relay or the blower motor. However, going from 4 to 5 makes a clicking noise not sure if that's normal or not

 

[CaptainXL]

5 went out on me twice before I replaced the connector. Had to replace both connector and resistor pack at the same time. GM actually has a service bulletin stating that both need to be replaced.

But now we know that you should still check the amp draw to see if the motor is the cause. My guess is that you will end up needing all three parts. At least thats what it starting to look like.

Still, dont take my word for it. You still need to troubleshoot the wiring and amp draw before making a decision.

 

[The_Roadie]

The motor power goes through a relay, and speed 5 does change its state, so the clicking is expected. I suspect the design was influenced by thoughts of having a redundant power path, so in case one path failed, you would still have SOME blower function available. Either for defogging the windshield for driver visibility in high humidity, or keeping the heat or AC going in times of extreme temps. Both of which could be a way for GM to avoid potential legal liability and a forced recall by the NHTSA.

 

[wesman43]

Alright, I'll do that today in my free time :3

 

[AtlWrk]

The motor power goes through a relay, and speed 5 does change its state, so the clicking is expected. I suspect the design was influenced by thoughts of having a redundant power path, so in case one path failed, you would still have SOME blower function available. Either for defogging the windshield for driver visibility in high humidity, or keeping the heat or AC going in times of extreme temps. Both of which could be a way for GM to avoid potential legal liability and a forced recall by the NHTSA.

This also has the high current path of setting 5 bypass both the ignition switch and HVAC control module. The HVAC control module's terminals are rated for even less current than the resistor pack.

Think about the hell that would be raised if it was HVAC modules failing like this instead of resistor packs...

 

[CaptainXL]

This also has the high current path of setting 5 bypass both the ignition switch and HVAC control module. The HVAC control module's terminals are rated for even less current than the resistor pack.

Think about the hell that would be raised if it was HVAC modules failing like this instead of resistor packs...

Yep that would be crazy expensive.

So basically he can rule out the HVAC module if the relay is being energized on speed 5. He can also rule out the 40 amp fused circuit. To me it seems like the only thing to blame would be the motor that's causing too much current for the wire to melt. And if the relay on the resistor pack is cheap the motor could take that along with it. That's why I think all three might need to be replaced.

 

[wesman43]

Yep that would be crazy expensive.

So basically he can rule out the HVAC module if the relay is being energized on speed 5. He can also rule out the 40 amp fused circuit. To me it seems like the only thing to blame would be the motor that's causing too much current for the wire to melt. And if the relay on the resistor pack is cheap the motor could take that along with it. That's why I think all three might need to be replaced.

Okay so let me get this straight: The relay is built into the resistor pack?! I'm sorry to be so ignorant, I have never really done anything with wiring except change out the blower motor in my other car lol, and build computers..I can do that too. And the three parts you are talking about that you suspect would be

A. Blower Motor
B. Resistor Pack
C. harness

 

[CaptainXL]

The relay is indeed built into the resistor pack. It's the black rectangular bulge on the backside where the connector is. When you select speed 5 on the hvac head unit it sends +12vdc to energize the relay and allows full battery voltage to go to the fan through a 40 amp fused circuit. It's all in the Chilton or service manual wiring diagram.

If you hear the click from the relay and it still doesn't work on speed 5 then the connector is fried and needs to be replaced. That is what happened to me. I replaced the resistor pack and got back speeds 1-4. But no 5. Then scratching my head I replaced the resistor pack again to still find speed 5 inop. So came here and learned about replacing the connector.

 

[wesman43]

The relay is indeed built into the resistor pack. It's the black rectangular bulge on the backside where the connector is. When you select speed 5 on the hvac head unit it sends +12vdc to energize the relay and allows full battery voltage to go to the fan through a 40 amp fused circuit. It's all in the Chilton or service manual wiring diagram.

If you hear the click from the relay and it still doesn't work on speed 5 then the connector is fried and needs to be replaced. That is what happened to me. I replaced the resistor pack and got back speeds 1-4. But no 5. Then scratching my head I replaced the resistor pack again to still find speed 5 inop. So came here and learned about replacing the connector.

My situation is different though, I get number 5 back every time I replaced it, that's why I did it 3 times to make sure I didn't get a bad batch or something because 1 day later on each of them, it would go back to no #5, could the connector still be involved in this?

 

[CaptainXL]

Couple thoughts here...

Perhaps if you follow that harness towards the hvac head unit you will find some messy splicing from a previous repair of the same issue? I don't know.

Could also be that the motor is frying the resistor pack without affecting the wiring? I have no concrete evidence, nor experience that this ever happens.

However, the issue you have sounds like what happened to me in a way. What could be happening is you are reseating the connector on a new resistor pack which cleans the connection of carbon. Have you tried to reseat the connector on the resistor pack first before trying a new one?

Also, I would make sure you are using an ACDelco resistor packs of the correct part number.

If you wish to tempt fait and not troubleshoot the wiring you could replace the $10 connector as GM says to and hope for the best. But I would definitely get the motor amperage.

 

[CaptainXL]

I own this one. Sears.com

Just got the clamp meter for Fathers day. Its nice.

View attachment 28973

 

[Team Dougherty]

Just got the clamp meter for Fathers day. Its nice.

View attachment 15518

You will be measuring all kinds of things now.