Please help with unusual blower motor resistor problem

767Jockey

Original poster
Member
Apr 5, 2012
30
Hi, new guy with my first post here on GMT Nation. I was an occasional user of the "other" site, but I'll be gere for now on. As for my issue, my heater/air conditioner blower fan control went from perfect to completely dead in an instant. I parked and it was perfect, I came out and it was dead. I didn't lose a speed or two at a time like I have read on other threads. So, I did a search, and decided to gamble on replacing the resistor pack. The job was just as easy as described, and the connector had very, very minor marks on it. I wouldn't call it melted or damaged. The problem now is, all speeds work EXCEPT for 5, the highest speed. Again, all speeds worked perfectly before it went totally dead. My guess is that the resistor pack that I installed (Autozone) is defective. Does anyone have any experience with this? Is there anything other than a defective resistor pack that can cause this, to go from dead, to everything working with a new pack except fan speed 5? Any help would be greatly appreciated. Thanks.
 

christo829

Member
Dec 7, 2011
509
Fairfax, Virginia
So you didn't replace the connector? If I'm recalling correctly, speed 5 pretty much bypasses the resistor array, and puts full voltage
through to the blower motor. The connector may look OK, but there may be some play inside the connector, allowing either a
bad connection or corrosion/tarnish to build up on the connection. The heat from a failing resistor pack can cause less than
obvious damage to the connector.

Check the internal condition of the connector for movement of the metal connections, or any small bit of melted
plastic that may have gotten on the metal.

It is possible that the resistor pack is defective, but check the connection closely first.

Good Luck!

Chris
 

djthumper

Administrator
Nov 20, 2011
14,956
North Las Vegas
Your other resistor pack is probably good. I am going to say it is the connector since high doesn't use the resistor pack.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Check underhood fuse #35. It is ONLY needed for speed 5, and its failure will affect no other function.

The resistor pack could also be bad, since it's a relay on the resistor pack that brings power from fuse #35 TO the motor.

If you have a meter, you could troubleshoot it properly, or just check that fuse first.
 

767Jockey

Original poster
Member
Apr 5, 2012
30
the roadie said:
Check underhood fuse #35. It is ONLY needed for speed 5, and its failure will affect no other function.

The resistor pack could also be bad, since it's a relay on the resistor pack that brings power from fuse #35 TO the motor.

If you have a meter, you could troubleshoot it properly, or just check that fuse first.

Well, I finally made it home to investigate further. Fuse #35 is fine. All speeds work except for 5. I have a meter, how do I properly troubleshoot this? I guess I have to check for voltage at the plug, what pins should show what voltage? On which pin do I place the ground (black) from the meter? Thanks!
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
767Jockey said:
Well, I finally made it home to investigate further. Fuse #35 is fine. All speeds work except for 5. I have a meter, how do I properly troubleshoot this? I guess I have to check for voltage at the plug, what pins should show what voltage? On which pin do I place the ground (black) from the meter? Thanks!
Put the black meter lead on a good ground elsewhere under the dash on metal. Trace the signal from fuse 35 to the resistor pack.

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767Jockey

Original poster
Member
Apr 5, 2012
30
Electrical is my weak point. I have no idea how to do that. I guess that with the black wire from the meter on ground, at least one of the pins on the plug for the blower motor should show 12v. If none of them do, I guess I'll just replace the blower resister again. That's about as far as my electrical troubleshooting skills go.
 

AtlWrk

Member
Dec 6, 2011
674
767Jockey said:
Electrical is my weak point. I have no idea how to do that. I guess that with the black wire from the meter on ground, at least one of the pins on the plug for the blower motor should show 12v. If none of them do, I guess I'll just replace the blower resister again. That's about as far as my electrical troubleshooting skills go.

It'll take 2 minutes to narrow this down:

(1)
Pull the resistor pack connector and use your meter to check the following:

Black meter lead on the BLACK wire's terminal.
Red meter lead on the RED wire's terminal.

You should always have +12V here at any setting with the car on/off.
If you don't, check fuse 35 again (swap it with a good fuse of the same value just to rule it out).
If you still don't have power than you have a problem with the harness and/or conntector itself.

(2)
If you do have +12V on the red wire:

Turn the ignition on and change the HVAC setting to HIGH.
Black meter lead on the BLACK wire's terminal.
Red meter lead on the ORANGE wire's terminal.

You should now have +12V on the orange wire.

If both (1) and (2) show that you have +12V when you're supposed to the controls and harness are not at fault. Then, and only then, would I suspect a bad resistor pack. It does happen.

Let us know what you find...
 

767Jockey

Original poster
Member
Apr 5, 2012
30
Wow, AtlWrk - that's exactly what I was hoping for. I can't thank you enough. I'll give it a shot tomorrow.
 

mitch

Member
Feb 21, 2012
8
This just happened to me today, I hear an audible clicking when switching fan to 5 but nothing happens. I'm going to examine it tomorrow.
 

CaptainXL

Member
Dec 4, 2011
2,445
A few months ago I had to replace the connector to get speed 5 to work. It was melted. I replaced the resistor pack as well since I was under there even though the resistor pack was not the problem.
 

767Jockey

Original poster
Member
Apr 5, 2012
30
AtlWrk said:
It'll take 2 minutes to narrow this down:

(1)
Pull the resistor pack connector and use your meter to check the following:

Black meter lead on the BLACK wire's terminal.
Red meter lead on the RED wire's terminal.

You should always have +12V here at any setting with the car on/off.
If you don't, check fuse 35 again (swap it with a good fuse of the same value just to rule it out).
If you still don't have power than you have a problem with the harness and/or conntector itself.

(2)
If you do have +12V on the red wire:

Turn the ignition on and change the HVAC setting to HIGH.
Black meter lead on the BLACK wire's terminal.
Red meter lead on the ORANGE wire's terminal.

You should now have +12V on the orange wire.

If both (1) and (2) show that you have +12V when you're supposed to the controls and harness are not at fault. Then, and only then, would I suspect a bad resistor pack. It does happen.

Let us know what you find...

Everything checked out exactly as you said. Red wire has 12V all the time, and the orange has 12v with key on and fan in speed 5. Looks like a bad resistor pack from Autozone. Can anyone think of another thing to check before I pull it out again?
 

767Jockey

Original poster
Member
Apr 5, 2012
30
the roadie said:
As long as you had the meter ground lead on the connector's black wire and not the frame or somewhere else, you've got it pegged.
Yep, black meter lead was in the connector that the black wire ran into. Looks like a bad part from Autozone. Thanks, all - great site!:thumbsup:
 

767Jockey

Original poster
Member
Apr 5, 2012
30
I had placed an earlier post / thread about my blower issue. It went from working perfectly on all speeds to completely dead on all speeds in an instant. One day it was working, the next day it was dead. Using all the great help that I received on this site, I went to AutoZone and bought what seemed to be the agreed upon fix, a new blower resistor. I installed it, and it worked perfectly, EXCEPT that fan speed 5 does not work. All the others, speeds 1 - 4 now work perfectly. I suspected I had received a bad part, but before just throwing a new part at it, I got some good advice from the great guys on the forum here, and did what I thought was a good job of troubleshooting. I first checked fuse #35, a big clunky looking thing of a type I've not seen before. It looked good visually. I then removed it, and used another fuse in it's place to check. The fan still didn't work with the other fuse in place. I then got great instructions on how to check for proper voltages. With the black meter lead on the black wire on the plug, I checked for 12 volts at the red wire. I have that with the key either on or off, which I'm told is the desired result. I checked for 12 volts at the orange wire with the key off. There is none, as it should be. I then turned on the key and turned the fan control to five. In that condition, I have 12 volts at the orange wire, which is correct.

So, based on all that, I pulled out the resistor again, returned it to Autozone, and got another. I put it in, eagerly turned on the car, flipped the fan control to 5, and.......(drum roll)..............nothing. It's still dead.

Any ideas, anyone? I'm no expert, but it seems to me that with voltage at the orange wire with the switch in position 5, then the fuse, harness and switch are fine. The motor has to be good, or it wouldn't turn at all on speeds 1 through 4, no? I'm lost. Any help on this would be GREATLY appreciated. Thanks.
 

767Jockey

Original poster
Member
Apr 5, 2012
30
767Jockey said:
I had placed an earlier post / thread about my blower issue. It went from working perfectly on all speeds to completely dead on all speeds in an instant. One day it was working, the next day it was dead. Using all the great help that I received on this site, I went to AutoZone and bought what seemed to be the agreed upon fix, a new blower resistor. I installed it, and it worked perfectly, EXCEPT that fan speed 5 does not work. All the others, speeds 1 - 4 now work perfectly. I suspected I had received a bad part, but before just throwing a new part at it, I got some good advice from the great guys on the forum here, and did what I thought was a good job of troubleshooting. I first checked fuse #35, a big clunky looking thing of a type I've not seen before. It looked good visually. I then removed it, and used another fuse in it's place to check. The fan still didn't work with the other fuse in place. I then got great instructions on how to check for proper voltages. With the black meter lead on the black wire on the plug, I checked for 12 volts at the red wire. I have that with the key either on or off, which I'm told is the desired result. I checked for 12 volts at the orange wire with the key off. There is none, as it should be. I then turned on the key and turned the fan control to five. In that condition, I have 12 volts at the orange wire, which is correct.

So, based on all that, I pulled out the resistor again, returned it to Autozone, and got another. I put it in, eagerly turned on the car, flipped the fan control to 5, and.......(drum roll)..............nothing. It's still dead.

Any ideas, anyone? I'm no expert, but it seems to me that with voltage at the orange wire with the switch in position 5, then the fuse, harness and switch are fine. The motor has to be good, or it wouldn't turn at all on speeds 1 through 4, no? I'm lost. Any help on this would be GREATLY appreciated. Thanks.

Anyone.......?????
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Voltage can appear on a wire and not have enough current available if it's a corroded connection to run the motor. Try measuring the voltage at the motor with it plugged in. You may find a bad ground.
 

CaptainXL

Member
Dec 4, 2011
2,445
767Jockey said:
Anyone.......?????

As stated before my recommendation would be to replace the connector going to the resistor module. When the wires get melted the plastic wicks its way into the crimp, burns and you get an intermittent electrical contact.
 

christo829

Member
Dec 7, 2011
509
Fairfax, Virginia
CaptainXL said:
As stated before my recommendation would be to replace the connector going to the resistor module. When the wires get melted the plastic wicks its way into the crimp, burns and you get an intermittent electrical contact.

Seconded. You can get a voltage reading from the connector when you stick the probe in, but
that doesn't tell you how well the connector is completing the circuit to the resistor pack. If that
pin is corroded, has plastic on it, or is slightly loose, that can affect how well it connects.

As the Roadie suggested, check voltage at the motor. You may still be getting voltage, but not enough current.

Cheers-

Chris
 

mitch

Member
Feb 21, 2012
8
I changed my resistor assembly and the connector at the same time. Check my article submission thread for what it looks like when the connector melts into the resistor pack. This is most likely your problem.
 

Mike

Member
Apr 8, 2012
42
mitch said:
I changed my resistor assembly and the connector at the same time. Check my article submission thread for what it looks like when the connector melts into the resistor pack. This is most likely your problem.

man, that was awesome. i bookmarked that link for when i decide to fix mine.
 

767Jockey

Original poster
Member
Apr 5, 2012
30
The bad news is, I haven't fixed it yet, just haven't had time. The good news is, I know what it is. Today, all speeds completely died again. It was 90 degrees out, the car was like an oven, and my wife was more than a bit irritable - just the thing to get a guy motivated!:biggrin:

On a hunch, I dropped the glove compartment down, reached in and wiggled the connector underneath - the 7 pin one. Bam - it worked!!! I put it on speed 5, wiggled again, and it worked as well. It's the connector. Thanks for all the help, guys. I just wanted to report back so that is someone in the future does a search and has the same problem, they'll know what it might be. Great site, thanks again!
 

767Jockey

Original poster
Member
Apr 5, 2012
30
I just realized that after all the support I got here, I failed to report back a definitive end to the story. I finally got around to replacing the connector, and all is well. Just wanted to close the loop on this so that in the future if anyone reads this for help with the same issue, they can see what happened to my vehicle. Thanks again for all the help.
 

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