When I bought my 928GTS it was winter and by the time the salesman told me the air conditioning was perfect. But it was not.

Since that time (two years ago) I sought the problem was on the gas. So this year after a long period of garage (TB job, X-pipe, etc) I decided to refill the system.

Once at the refill machine we noted that there was a pressure of 3 bars (45PSI) on the system. So I left it as it was and started to find the possible cause for not having cold air.

I did not find it up to now and I already disassembled the entire center console.

This is a resume of the symptoms:
- There is no cold air with AC turned ON.
- The compressor works when I turn ON the AC.
- I can see, through the visor, some liquid inside the Gas tank in the front of the radiator.
- There is a leak on the vacuum system when I turn the AC ON or when I select the recycle air position. (I can hear the leak. I did not reach, yet, the recycle flap)
- I touched the evaporator trough the inner vent opening and it is not cold.
- I touched the expansion valve and it is not cold.

For the looks I think that the gas is either old or not enough. But I don't want to loose 75€ to refill it without checking other possibilities.

Any idea to fix it?

Thank You

 

Expansion Valve, what are your low and high side pressures?

 

What do you mean there was 45PSI? Was that on the low side when you had the A/C running? If it was 45PSI with the car off, then you do not have enough charge in the system for cold air at all. Even with a leak, there is usually residual pressure inside the system, or the leak is small enough that it will only leak if it's above a certain pressure.

Dan
'91 928GT S/C

 

If the low side was showing 45PSI that's is almost a perfect level of refrigerant in the system if the engine/compressor were running. I think Tampa928s is onto something with his guess that the problem is related to the expansion valve. But he's merely guessing as are the rest of us because we need to know the pressures on both the high and low sides as well as the ambient air temperature when the pressures were checked.

A leaking vacuum diaphragm will not prevent the expansion valve and evaporator from getting cold.

 

Thank you for your answers

The 45 psi were measured with the engine off at the connexion located on the reservoir (High pressure line I suppose)

 

That's what I thought. This is definitely too low. With the engine off you should be seeing around 100psi or more on both the low side and high side. The A/C tech should have known this too. So not only are you low on freon, but you have a leak that you should find and fix before you try to recharge the system again. Also, freon does not get "old" and should never be replaced. It should also never need to be recharged unless there is a leak.

Dan
'91 928GT S/C

 

+1

 

I'm also suprised that the compressor will come on with that low of charge. Does it click on and off. "Short cycling"?

 

No, with ~45psi at rest in there the pressure is not low enough to trigger the low pressure switch. The compressor will run all the time. The purpose of this system is to not run the compressor when there is no freon inside because it is the freon that carries the oil that's necessary to lubricate the compressor. With that level of pressure in there, there is still enough freon to circulate the oil.

Dan
'91 928GT S/C

 

The first thing to do is have your shop reclaim the freon then vacuum down the system or 1/2 hour min. It should hold at about -28 to - 30 with the valves on the gages closed for hours. If you loose the vacuum you have a leak which must be taken care of. Your static pressure 45 Lb's should be around 80Lbs or so. If your low on freon do what I suggested first before you waste your money.

 

Thank you all.

I will go back to the AC mechanic.

This car was parked 4 years before I bought it. So during this time there might be some o-ring leaking due to age.

With this information I will be more comfortable to go there and ask for the leak repair.

 

Miguel,

Also check
- if the comb flap is working (comb is up when temp slider is all the way left)
- if the heater valve is closed (ergo not letting any hot water through from the engine to the heat changer in the HVAC).

Cheers