2nd Gen Non-Engine/Transmission AC compressor won't start

[Dennis Garrett]

The AC on my 97 has worked fine over the years, and just noticed in the last couple of days, the compressor won't start now. I checked the fuse & relay in the power distribution box next to the barrety,a both look OK. I have no reason to believe it's low on freon, but haven't had that checked yet. Anything else to check? (It's too cold to mess with it much right now, but I like to run it while warming the truck up, it puts a little load on the engine, and takes the moisture out of the air when I'm trying to defrost)

 

[Bob Beauchaine]

Dennis

The way most R134A systems are set up when your refrigerant charge goes below about 55 to 60 % of normal the compressor shuts off to protect itself. There is a good chance that you are low on freon. You can by pass the low PSI switch as a test. That should give you an idea if the compressor is OK - it should be.



If you have access to AC services the best route is to evacuate, refill and test the system. That way you will know how good your system is. I have seen very few with major problems with these systems.



You can also purchase R134A in most parts stores and it will have a dye in it to pinpoint leaks. Just follow the directions and you should be OK. Hope this helps.



Bob

 

[B.G. Smith]

I believe the ambient air temp. is by-passed in defrost position, hit defrost and see if it comes on, The low pressure switch is for compressor protection and would not be by-passed. Correction! bg

 

[Dennis Garrett]

I tried it in the defrost position, still nothing, It might be just too cold for it to come on. Might have a low temp thermostat built in someplace. I've really never noticed if the compressor actually came on in cold weather or not. Today it's supposed to go up above freezing so maybe it'll work. If not, it may have leaked down somehow.

 

[SRadke]

Check the horn fuse. The AC clutch is routed throught that one. Don't know why?



-Scott

 

[jgallentine]

Bypass the low pressure switch as a test as recommended above!



My 99 is currently out of refrigerant due to a leaking evaporator core under the dash and the AC pump will not come on in AC or defrost.