Well took the truck in and the compressor was shot. They replaced compressor, but now the compressor runs constant regardless of what the system is set at. He said i should take it to the dealer for a computer reprogramming.....what does that cost???
Damn it there is no reprogramming. If the compressor never shuts off even with the a/c fuses pulled you either have a 12v+ shorting to the a/c request circuit to the PCM or the PCM is damaged or the clutch relay is shorting causing a constant voltage feed to the clutch. or the head unit has suffered damage as is sending a A/C request to the PCM regardless of switch position. Look at some of the previous A/C posts where I have wiring diagrams posted for help tracking it down. If you need troubleshooting charts for a specific issue let me know and I will forward what I have.
I've had a similar problem - fan control either erratic or none at all. I replaced the switch and found some heat damage to the connector. The new switch worked perfectly ... for about a minute and now its dead. The fuse is not blown, and there is no evidence of heat damage to the new switch, when I pulled it out to check it.
Why is Off/Low/Medium/High on a 12 volt DC motor so complicated?
I pulled the resistor and it looks clean and shiny, but I have no way to check it.
Thanks, Sunlitcomet. Yup, all speeds are dead. Its a '97 Tahoe 1500 LT 4 WD 4 door.
The plug-in part of the wiring harness was a bit melted, and insulation on the brown wire was melted back about 1 mm, but the wire looked in tact. I cleaned up the contacts on the plug the best I could, but it wasn't perfect.
The heater HVAC fuse is OK. I pulled out the switch wiring harness and cleaned the plug contacts very well and put it all back together. Low speed - OK, Med - OK, High -OK, Off - OK ... then dead as doornail again!
What does the relay near the resistor do, and could that be the culprit?
I give. Having replaced the switch, $24, the relay, $25, and now th resistor, $35, but still no joy. Anyone know if I can jury-rig an on / off switch with 12v DC directly to the blower (which I know works) through the two female clip leads on the blower to make it work. One lead is purple and the other black. Hoping its positive and ground sounds way too optimistic, as the motor is likely grounded to the frame. All I want is the defroster and heater to work on this old clunker. Any advice would be appreciated. Thanks.