AC/heater problems with 1990 Avantis...possibly '87-'90s.

[Jim Baize]

OK. This is a weird topic, I suppose. I purchased a 1990 4-door and the AC wasn't working. The first guy I took it to put on a new compressor (it did need one) but it never did cool very well in the passenger compartment. The freon was already converted to 134 and is full. The second shop did nothing and charged well for it. It has been in the third shop (Chevy dealership) for about 6 weeks and there seems to be no progress. Rich Morris and I think it may be the Climate Control module. The correct part number is 16080732. I have a few other units that LOOK the same, but have different numbers and do not work. It is possible that all of them are defective. It is also possible there is something else wrong. The heat doesn't heat up, even when I set the temperature to 90° but the AC compressor runs! When I set it to 60° the fan runs full speed, but doesn't cool the compartment on warm days. We have looked at the "programmer" (the unit with solenoids and vacuum hoses.) It may be that. The Climate Control is from an 89-90 Pontiac Bonneville and there are reports of AC/heater problems on those GM cars. I have no idea what to do, so...

Rich and I are looking for electronic techs to test out the original Climate Control units.

Or we are looking for new (or known to be working) units numbered 16080732.

Anyone have any ideas?

I have checked with John Hull about parts. I have also checked with Ernest Edwards. Any other ideas out there?

Jim Baize

[IndyJimW]

The first guy I took it to put on a new compressor (it did need one) but it never did cool very well in the passenger compartment. The freon was already converted to 134 and is full.

R134a won't cool as well as R12. You need a charge of about 80% of R134a compaired to R12. If your Avanti is like mine the orginal charge is unknown, so you will have to watch the gauge pressures or measure the temperature difference between the inlet and outlet tubes. The difference should be about 2 degrees or as close as possible.

The heat doesn't heat up, even when I set the temperature to 90° but the AC compressor runs!

Do you have flow in and out of the heater core? I usually just grab the heater hoses and see if one is cooler then the other. The A/C compressor will run when in defrost mode.

When I set it to 60° the fan runs full speed, but doesn't cool the compartment on warm days.

Sounds like the charge is not right. Place a thermostat in the center vent, turn the A/C on high and open the doors. Place another thermostat about 1 foot in front of the car. The difference of a good working A/C should be at least 30 degrees.

If it was in my shop I would start with the basics.

1 - Check operation of the different modes. A/C - Heat - Defrost - and take some temperature readings at the vents and outside.

2 - Correct the R134a charge.

3 - Test coolant flow to heater core You may have a vacuum operated shut off valve in the heater hose that is stuck shut or a clogged heater core.

Once I was sure the basic system COULD operate I would then look at the controls.

If your HVAC system is like my 1987 Avanti is was border line when new. Add 25 years and conversion to R134a and cool may be the best it will perform.

I have removed the orginal HVAC system, a cobbled up afair at best, and am installing a Vintage Air Gen IV system in my 87.

Happy motoring,

Jim Wood

[Gunslinger]

Another possible issue is the condition of the seals and ducting for the a/c. If those are deteriorated due to age, much of the blowing air is cooling the inside of the dash rather than out of the vents cooing the car interior. I had a Corvette that did that...the system was providing cold air...it just wasn't getting to the vents.

[IndyJimW]

Part # 16080732 is coming up as an engine ECU.

Alldata lists for 1989 Pontiac Bonneville a Control Module HVAC PN 16060824 or AC Delco 15-71538.

No TSB for that problem.

GM is showing 2 HVAC systems for Bonneville. One vacuum operated the other is electronic.

Will need more info.

Happy Motoring,

Jim Wood