Seen a few treads talking about heater only, original AC, or heater trucks converted to AC with this problem. Also, some posts that the switch and connector is roughly replaced every two years.
My truck is AC original, though not sure if the wiring was ever been replaced. The AC has been converted to to R134a but that work was all in the engine bay and I don't think that conversion had any effect on the AC/Heater User Fan Control switch.
- My switch was a little flaky when I got it, meaning sometimes I had to move it up and down to get the fan to turn on. I just let it slip my mind to replace the switch, as it didn't really happen a lot.
- Thursday~Sunday, I went on a long trip. 8 hours trip (4 each way) with hours driving around in East Texas during a car tour. So likely 16+ plus with the fan mostly on one notch below high.
- One hour before getting home, after filling up, I couldn't get the fan off low speed. Also, the switch was not moving up/down very well. After a bit I did get it on the higher speed. I instructed my daughter, don't touch the fan switch!
I have ordered a new switch from GMC Paul's but I just had a though that I should check under the dash too. In other posts I have seen worse connectors but I'm am pretty sure I'd want to replace the connector too. Though some of the damage has gotten to the wire insulation - some shrink tube might be a okay solution for that, I hope. When I got home, I did turned the switch to the off position and this morning it is pretty much stuck/frozen in the off position now.
Sooo - I can't seem to find a consensus on the various threads/postings about the cause of this. Some say perhaps a bad ground or just replace your switch? I assume once I get my switch in, the fan will fire right up. I haven't any problems with the fan speeds (like the other posts about a resistor) or at least not until things got all melty. Which isn't really the connector but the switch inside.
Thanks to anyone who has had / seen this issue and has moved past it. Though I suppose you would have had to have the truck for a LOT of years and a LOT of AC useage to know the melting went away.