Looking for input in trouble shooting rear A/C only blows hot air on a 1991 Chevrolet G20 van Aero conversion. Once fixed, I will then post in “What did you do to your van today” section….


Here is what I know with the A/C.

1. Installed new compressor last year, R134a
2. Charged the system up to 4lbs.
3. Ran OK last summer (worked, but just didn’t have the power/cold of a newer vehicle, I know it’s 28 years old and there have been a few improvements in 28 years, I also understand the van is a large area to cool down on a HOT Iowa day)
4. As of last night, the front blows cold air when the AC is turned on, the rear blows hot air.

Here is the issue and what I don't know

1. The rear AC only blows hot air, at first, I thought the rear needed a little time to cool down
a. Blower works great
Rear air worked last year on the way to “Van Nationals and back”. First time using the rear air this year (last night) would only blow hot air. From reading your posts (I’m not a mechanic, but enjoy a good trouble shooting with a voltmeter) it sounds as if I may have 1 of the following causing my problem.

1. Valve up in engine compartment that is allowing coolant to still flow to rear, thus why rear a/c is blowing hot air.
a. Can a person shut this OFF? If so how?
b. Where is the valve located?
c. Does anyone know if that valve is vacuum operated or DC operated?
2. Could I have a bad “expansion valve” in the rear A/C?
a. If so, how does one test the expansion valve?
I would like to say the issue is #1 but would like anyone’s input before I tear into it this weekend and get soaking wet from the humidity this weekend.