A/C just quit....A/C was working when I shut off the truck....went into a store, 20 minutes later started the truck, no A/C. No power to the A/C switch on the dash, or the recirculate switch, or the A/C, defroster, vent position switch...which is stuck on vents. Checked fuses and relays that appear to control the A/C....all good.
What am I looking for and where do I look ??

Regards
Gemstone

 

Had a similar situation...had to replace the a/c compressor.

 

I don't see the connection between a defective compressor and no power to the dash switches....what am I missing ?

Regards
Gemstone

 

If the clutch on the compressor fails to engage, then the on/off fan speed switch on the dash and related parts like the vent controls and defrost will not work. When the clutch fails then the rest of the system will act like there is no power...it is all linked together.

I am suggesting that this 'may' be an issue to have checked out. My a/c did the same thing...was working one minute and then suddenly nothing. Checked the fuses and switches and ultimately it was the clutch on the compressor that had failed.

Also, if the ECM senses low pressure in the low pressure fluid line, it will stop the compressor clutch from engaging to prevent any damage. This will also cause the dash controls to not work.

 

Not meaning to steal the thread but I have some ??, too. What's the low pressure fluid line and where is that switch? I've been having problems with the compressor stopping for no ryhme or reason. Can go 100s of miles, cooling great, I slow down for a town or corner and it stops. The only switch under the hood is the trinary sw. on the disc. line. I replaced it and no change. I'd sure like to know what other pressure or temp controls it has. I can't find anything else. Ive watch the gauges for a long time and tried all engine speeds, windows up/down for different loads and never see any reason why the comp. needs to shut off and have to be manually reset by cycling the fan or comp. switch. TIA! Craig

 

There is a diode in the wire harness on AC comp. I had one go bad and stopped my AC. Had to get a new compressor.

 

Yeh, I've read about that diode. Whatever is making mine quit, I think, is inside the dash or it's the puter. I wish I knew how to check all the puter I/Os. I can jumper 12v. to the clutch wire that's under the big wire plug cover next to the master cylinder and it pulls in. That's my back-up, for now! Craig

 

"I can jumper 12v. to the clutch wire that's under the big wire plug cover next to the master cylinder and it pulls in".....

So, what color is that clutch wire ? I assume you are talking about the wire plug to the left of the master cylinder....

Regards
Gemstone

 

Yes, the dust cover snaps off, exposing the wires. The screw in the center pulls the plug together and pushes it apart if you unscrew it. Not necessary to unscrew it. It's the dark blue with a black tracer. It's in the far left vertical row and the 3rd wire from the top. I can't guarantee it's the same on your 05. The wiring in my friends 03 isn't even identical to my 03! Craig

 

"The wiring in my friends 03 isn't even identical to my 03!".....

Great....but thanks, It gives me a starting point, and as long as the jumper will engage the clutch, it gives me a way to eliminate the compressor as the problem....

 

I crawled underneath and found the clutch wire on the compressor and then I found that wire in the big plug. Mine was working fine when I did that so I could use a test light to verify.Craig

 

The defective part was the dashboard A/C switch cluster.

Thanks to all for the replies.
Gemstone

 

What all is in the cluster? A puter? I just got a service manual disc but haven't had time to use it much. It mentions a JTEC - I'm assuming a puter or master control, somewhere. There IS a fin probe in the evap to prevent freeze-up. I already knew there was something like that from watching the lo-side gauge. I was about ready to get into that cluster but I talked to Mark@TST yesterday and I need to move the ground wire for the PMCR. I had already put the PMCR into bypass and the AC glemilins went away, so the problems have been PMCR related. I only drove a few miles and the AC worked perfectly but I'm not absolutely certain there's no other problem but it sure looked promising. For some reason, aftermarket lift pumps and the PMCR require a different ground path than a truck with the oem pump. I'm getting ready to go to the UK. I'll try it in a couple of weeks. Craig