I have already had the plug and resistor thing done to my truck after I lost a few speeds on the dial, and all has been well for the past 2 years. Yesterday, after running back from upstate NY (about 4 hours) with the ac on I stopped home for an hour, took a 35 minute ride with AC on, stopped for 15 minutes. Got in the truck started it, drove out the lot and flipped the fan switch to #1, ac came on, drove 40 feet ,heard a pop and the fan went up to max speed, ac light was blinking, turning the speed dial did nothing, hitting the ac switch did nothing, turning the speed dial to off did nothing ! 15 seconds later it was back to normal, all fan speeds work,ac works fine. What gives??? Failure imminent? Any thoughts?
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AC went crazy yesterday??
- Thread starter Bammer
- Start date
- Staff
- #3
It seems you have a short circuit somewhere John. It's gonna take a schematic and time to figure out. Have you talked to Joe? (If you do tell him Hi.)
3500GMC
What T F, over
May check out the amp draw of the motor or just replace it. Sometimes motors take out modules and resistors..
- Staff
- #8
Also find and check the ground for the module. I just went through this with a bUICK that was burning out modules, and it was a weak ground taking em out.
Will do, thanks for the tip.
millsroger
New Member
I see two things---one is the "pop", the other is running with key off. First, the pop---GM resistor units often have a thermal fuse for each resistor mounted on the resistor block. They are often directly under and quite close to the resistor itself. When these things reach a certain temperature they pop like a fuse-you lose that speed. Nothing wrong with the resistor itself.
This can happen when drawing outside air on a hot day and a partially clogged air flow. A draggy fan ups the current flow some more, also heating the resistor.
On the new resistor block, bend the legs on all the fuses so they are laying flat toward the middle of the block. On hot days use Recirculate so it is not drawing hot outside air--doesn't work so hard. Check for clogged core.
Running with the key off is prolly a failing relay--contacts may have gotten burned from high current switching and stuck. What speed it was running at will tell you which relay.
This can happen when drawing outside air on a hot day and a partially clogged air flow. A draggy fan ups the current flow some more, also heating the resistor.
On the new resistor block, bend the legs on all the fuses so they are laying flat toward the middle of the block. On hot days use Recirculate so it is not drawing hot outside air--doesn't work so hard. Check for clogged core.
Running with the key off is prolly a failing relay--contacts may have gotten burned from high current switching and stuck. What speed it was running at will tell you which relay.
- Staff
- #11
The new resistor packs and relay setups are hardly even recognizeable compared to the ones of old. Most of them are sealed units now with ehat sinks, and relays soldered onto the module.