Mike D

About a week ago I had the truck idling for about 45 minutes while hooking up the trailer and getting the load tied down. I had my hound in the truck and it was 90+ degrees outside. Anyway, after getting the trailer loaded and truck tied down, hopped in the truck and the A/C was blowing warm air out to just the defrost vent no matter where I put the selector switch. I kept turning the **** to different positions and the ac finally came back on.

I'm still having this problem flash up from time to time.

I've searched the forum and haven't seen this problem mentioned. I have checked all the vacuum line etc. and don't see a problem.

I don't know jack about AC, need some help to point me in the right direction.

I'll buy gauges to check the system if needed.

cappykd

I'd check your freon level before I wasted time and money trying anything else. Apparently the 2nd gens have know issues with the evap. leaking.

Busboy

If the "mode" doors change on you it IS a vacuum related problem. Now it could be that you have a bad vacuum door actuator or bad vacuum rotary sw but I would check again all the vacuum lines under the hood first. As for the blowing warm bit, at idle with no vacuum the recirc door would be open to outside air and if the hood seal is missing it would be taking air from under the hood as well as outside air, that coupled with the fact that the AC doesn't perform that well at idle could explain the situation. Again check the vacuum first

mrclean

As above, check your vac lines. Loss of vacuum will cause the HVAC system to "default" to defrost. Most common failure is under the driver-side battery, on the cruise control servo. Battery acid drips down onto the plastic vac tube, eats a hole in it. Hard to see even if you know to look there. Also, your system may need a jolt of refrigerant. Late model 134a systems seem to need some added every couple of years. HTH

Mike D

I checked all the connection under the hood and everything looks good. Outside of replacing all the vacuum lines and connections, not sure what else to do. Is there a vacuum tester that can be used?

I also took the glove box out, and looked at the silver vacuum operated canister that opens the door and it seemed to operate fine.

I'll check the refrigerant level as well. Thanks for the tips!

Busboy

Under the hood right by where the AC lines come through is a small BLACK vacuum line, this supplies vacuum to the rotary mode selector sw. If you have a vacuum hand pump the next time it quits you could hook the pump to the line going inside and give it vacuum. If the plenum modes return to normal then the problem is under the hood. If it quits only occasionally look for a cracked hard plastic line as it must be somewhat sealing enough to let things work.

haloman

I wonder if your compressor froze up and just needed to unthaw?

justme-

If anything in an AC system freezes up the gas is low- it will never happen on a properly operating system.

xtoyz17

Low freon, poor vacuum, or a number of other things. If you weren't switching door positions though I don't see how it would suddenly stop, and then start working after awhile again.

high bid

Yep, definately sounds like a vac line. I had the same prob w/a gasser. Double check all the rubber connections and plastic lines as the heat makes them brittle and they crack. The lines also have small plastic filter looking devices...these allow vac to go in one direction and help w/the open/close of the vent doors. good luck.