This is my first post and my first question too.I have a 98 Blazer with 170,000 miles and my ac compressor stays on all the time.No matter where the selector switch is positioned.I swapped the ac relay on the drivers side fender fuse/relay box and no change.I also unplugged the compressor and that worked.(thought clutch may be stuck)Anyway,you have any suggestions or ideas?Thanks

 

Here's a thought. Maybe your selector **** is broken internally just behind the dash and it broke selected to AC. I just pulled that out of my ***, but if anyone else out there that's actually had the dash off and thinks this is possible agrees, you might want to read up on how to take your dash off.

 

You need a refill on your AC. Try your AC, it will not likely work very good. Get it filled up and your all set.

 

Why would simply refilling the AC cause the compressor to only run when the AC is selected? It sounds like he's saying the compressor is running while his selector **** is in the off position. I'm by no means an expert, but that doesn't sound very intuitive to me.

 

Its the compressors way of telling you its time for a recharge. Mine does the same thing, I just haven't recharged it yet. So I unplugged it.

 

The a/c compressor should run in any a/c mode and in defrost mode. If it's running all the time there must be a problem in the control head or the wiring.
I have to go to work in a minute so I don't have time to look at the wiring, I'll try to have a look tonight.
If the system is low on refrigerant, the compressor will not engage, so I don't believe that it's a re-charge problem.

 

I agree,the air is cold.The compressor runs even in the off condition.So it could be the control head.

 

If the refrigerant is low then the comp. clutch will engage and disengage continuosly. Check wiring and switch.

 

Yes it will. My system is bone dry, and if I plug it back in it will engage and dissengage non stop.

 

If it is running in the OFF position then it does sound like a wiring or switch issue.