95 993 A/C issue

[Sjuliani]

Just started driving the car again which is a 95 993 C2 and the A/C doesnt blow cold air. The clutch on the compressor does kick in and it does blow air as it should but not COLD air. Had a good mechanic ran a 20 min leak test(passed), vaccumed the system for another 20 and finally recharged the system to the recommended 840g...after the recharge the system started to cool(not really cold but it was a improvement) for a while (around 12 hours) and then today it was just as it was before....
my question is the sticker on the back regarding the ac says that the maximum is 1,851lbs/840g...is that accurate 1851lbs? could the clutch on the compressor be gone (the car only has 30K miles)?

[Traveller]

Europeans use a comma in place of our decimals. You'll find that 1.851 pounds equates to 840 grams.

I just had an A/C issue...well not really an A/C issue in that the A/C was working, I just wasn't getting any cold air coming through the vents due to a flap that was not opening (you could hear this wheezing sound as I later found out owners called it).

In my case, a vacuum line had split that connects the main manifold with a check valve. Any vacuum leak associated with the ventilation system will cause issues.

If your A/C is working, you will find that one of the metal pipes coming off the compressor is ultra cold (mine was near freezing and covered in condensation) while the other one was quite hot.

[bazar01]

As traveller had stated, check to make sure the A/C is working by looking at the two lines going to the compressor in the engine compartment. One should be cold and sweating and the other is really hot and be careful. Best thing really is to hook up a gauge manifold to check system pressures, but since you probably do not have one, touching the bigger line to check if it is cold and sweating will be enough.

If the system is working, then you have a damper issue. It is either a heating damper is open allowing hot air from the heat exchanger to mix with the cold air or a cold air damper not opening. Do you have air coming out of the vents?

[kuehl]

It maybe the 20 minute leak test was the normal "vacuum" test performed to test for gross leaks while under vacuum. Passing this test does not insure your system is leak free.

If you had a refrigerant leak and it was not repaired you will continue to leak refrigerant.

Have your technician attach his gauge set again and report back the ambient (outside) temperature, and the low and high side pressures at idle.

Also have your technician use an electronic leak detector to sniff all the system joints as well as the condenser, compressor, drier area and especially the air vents in the car and the evaporator box condensation drain tube.

[Traveller]

Originally Posted by bazar01

Best thing really is to hook up a gauge manifold to check system pressures, but since you probably do not have one...

The A/C manifold gauges are on sale at Harbor Freight at the moment...for $29.99...half price.

[rsr91128]

Originally Posted by kuehl

Have your technician attach his gauge set again and report back the ambient (outside) temperature, and the low and high side pressures at idle.

Do you check these at idle? If so what are the hi/low numbers supposed to be at around 85 dg?

Only chart I have seen was with engine @ 2000 rpm.

TIA

[ed.trottier]

Having same trouble (thread) with my A/C. No "clicking" of check valve as usually happens as vacuum is pulled in accumulator. Is blue/black vacuum check valve (vacuum supply line off brake booster) an OEM 928 part? Or can they be bought at local Auto Zone??? Thanks, EHT

[kuehl]

Originally Posted by rsr91128

Do you check these at idle? If so what are the hi/low numbers supposed to be at around 85 dg?

Only chart I have seen was with engine @ 2000 rpm.

TIA

In a picture perfect world with R134a you can use the following nominal pressures (psi) at 85F:

low = 30
high = 214

These values are "nominal". You may notice them go up or down a few psi in either direction as the system operates due to various normal reasons, such as the expansion valve opens and closes, the compressor clutch cycles on or off with the thermostat. The front condenser fan turns on and off or changes its fan speed. Usually the low side is given a broader range than the high side and not noted in a Pressures and Temperatures chart but rather shown as between 20-40 psi. There various 'things' (good and bad) that affect the pressures so if you don't hit it on the head 'perfectly' then just say its not a picture perfect world.