A/C blower resistor now fails every four years, like clockwork

working on it · April 8, 2023

We have a '98 GMC 1500 that we seldom use, but mostly do in the summer, so the A/C needs to work. Right now, the fan is OK when we start out, but goes wonky after 10-20 minutes, as it always does, when the resistor fails.

We've owned it since '07, and I've had to refill the R-134A refrigerant every other year (slow leak somewhere), the control panel two years ago, the blower motor (& fan) once,and the blower resistor several times over the years. The last three were done 4 years apart, and it's time for another.

I've been using GM #15039098 resistor, so it should be reliable, and I just bought another one to install...should I also get a new blower motor (as the one currently installed is from 2010 or 2011), because it might be why the resistors (and control panel) have been failing?

I remember testing the circuits and amp draw when I replaced the resistor about eight years back, but the readings were as expected, IIRC, but that was long ago. Maybe the unused blower has gotten rusty inside, as it sits for months at a time, between uses (since 2016 or so).

newdude · April 8, 2023

High drag on the blower motor is a possibility if the bearing has been setting up over the years. Might be worth a shot.

working on it · April 16, 2023

Not the Resistor, after all!

Just installed the new resistor today, and recharged the refrigerant. However, the blower started failing while I ran it and recharged the R-134A...same as it did before the resistor swap...after running 20 minutes.

I jabbed/hit the HVAC control module (replaced two years ago) and the blower started working fine again. It is a Dorman unit, so I should've expected it to go bad. I took out the blower to bench test it, before I swapped control module and each time I've installed another resistor, and it's always fine (VDO blowers are great, IMO). The resistor I pulled is probably still good, so it's a spare now.

I'm going to slap the crap out of the Dorman part to make it work whenever the blower starts losing it, until it won't work anymore, then buy a cheap Amazon unit for half the price. I'm tired of this recurring problem, so I'm going to go cheap on it, and just pay the bare minimum for parts, since they all seem suspect these days.

working on it · May 22

On 4/15/2023 at 7:06 PM, working on it said:

Not the Resistor, after all!

Just installed the new resistor today, and recharged the refrigerant. However, the blower started failing while I ran it and recharged the R-134A...same as it did before the resistor swap...after running 20 minutes.

I jabbed/hit the HVAC control module (replaced two years ago) and the blower started working fine again. It is a Dorman unit, so I should've expected it to go bad. I took out the blower to bench test it, before I swapped control module and each time I've installed another resistor, and it's always fine (VDO blowers are great, IMO). The resistor I pulled is probably still good, so it's a spare now.

I'm going to slap the crap out of the Dorman part to make it work whenever the blower starts losing it, until it won't work anymore, then buy a cheap Amazon unit for half the price. I'm tired of this recurring problem, so I'm going to go cheap on it, and just pay the bare minimum for parts, since they all seem suspect these days.

It's that time of year, again, when I recharge the GMC's refrgerant and it blows cold air (38F when the ambient air temp is 90F). This year, I added a manually-switched, 12" diameter, electric puller fan inside the viscous fan shroud, to aid the A/C when idling at stoplights (idles at 550 rpm). It works as well as it ever did...until the blower starts cutting-out, and I switch it to high speed).

I installed yet another resistor (a Standard Motor Product) after last years' post (now I have two spares: a GM part, and a Dorman part), and it never helped. The control panel and blower are the same as last year, so I expected and received no improvement.

I spent over a grand in February (IIRC) on the GMC's tires and braking system, so I'm hesitant to buy another control panel and blower motor for my wife's back-up vehicle, which only gets driven an average of twice a month (more in the summer than in other seasons). I was just checking in here, to see if anyone had a similar experience with their truck, or could recommend a work-around.

Edited May 23 by working on it