Air con - Order to troubleshoot

Troubleshooting
1

Hi all, I’ve got a manual NA GTO (1990) and the air con is blowing lukewarm/ambient temperature. Hoping someone here may have some wisdom on how to figure this out.

I’ve been servicing and fixing things bit by bit since my ownership. However, the car was dry-stored for 10+ years so I’m open to likely age-related suggestions.

I would appreciate recommendations on the best order to troubleshoot and which parts are worth replacing given the age of these cars.

For context:

  • Aux belt is new.

  • Non-AC climate control features work, fan speeds, different blower directions, defrost etc.

  • Using the scan tool, the magnetic AC clutch seems to turn on and off with the engine speed wavering slightly as one would expect.

  • The climate control display has been repaired and has been working fine ever since.

  • AC had no gas left when purchased, I’ve fitted the r134a adaptors per Joe’s video and re gassed, no apparent leaks and refrigerant pressure still holding when checked with a gauge.

  • No o-rings have yet been replaced (silly I know but I wanted to see if the system held any pressure as it was).

  • The dryer hasn’t been replaced so is at least 10+ years old. Yesterday the sight glass seemed clear (not cloudy) and I could see refrigerant in it (appeared almost pale green?).

  • Dryer pic below is from a brief test today however I can’t see the greenish substance I could yesterday.

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  • Using the scan tool, there is an intermittent error code for one of the air mixture matrix blower things (see pic below). This is the only error code but doesn’t appear all the time.

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  • The main climate control read out from the scan tool is below:

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  • When I got the car, I noticed the AC fan fuse was missing so this has been replaced.

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This is the information I have so far. Any insight or recommendations on how to proceed would be greatly appreciated.

Elliott

2

The air mixer motor. Does your car blow cold air and move from hot to cold OK? Don’t need the AC once for this.

basically behind the AC display there is a little flap/ mixer motor that the either allows air to pass over a little radiator for hot air and bypass it for cold air. This was a problem on my car as the air was always on hot! I swapped the motor and you can test it before putting all the centre vents/ radio and ac control unit back by just setting to hot and cold and watching the motor move.

James

3

Thanks for the response. I think if my mixer motor is indeed faulty it would at least imply it’s not delivering the correct amount of hot air so the opposite of your case since it was fully cold but not fully hot back in winter.

In winter I was getting cold (ambient) air on the coldest setting and then warmish air on the hottest setting (I thought due to a clogged heater core). I’ll have a look to see if the motor is doing its job as that could explain things.

Ultimately, I think I’ll need a new compressor as all other AC specific components seem to be working and the unit itself sat without use for a decade.