surgiblade

In summer it reached 100 degrees F here.

First a huge thanks to Bill Ball for his valuable help- started out with tech tip of replacing heater bypass valve, which I hoped would do the trick. Then checked low and high pressure. then the vaccuum lines. Then took apart and fixed climate control so it would click on the microswitch at maximum cool. Then took to Quality imports, added 2.5 lbs freon. '

Still the A/C weaker than either of my toyotas or ancient minivan. Back to Quality Imports- rechecked-unable to find anything wrong.

Back to Bills today- off with glove box, adjustment of flaps and viola- No
warm air into vent !! (But still NOT cold like Bill's A/C.)

Called German Auto Clinic- told top go to Auto A/C place. Opem to ideas.

Mike aka surgiblade

docmirror

Expansion valve. Water/air in the system. Dryer/receiver old. Evacuate the system again. Have the expansion valve and dryer replaced. Evacuate the system COMPLETELY (sorry for shouting). Then add Freon. Also, check your heater valve is actually closing with vacuum. The armature rod should be pulled completely over and tight when the car is running. Now, with the AC on max, one click from the far left, crawl head first into the pass footwell, and look up BEHIND the glove box. Is the recirculating air door open or closed? If closed, you are drawing in outside air for AC, and the vacuum system that controls the recirc flap door need to be investigated.

If the car sat for any time with the AC system not sealed the dryer is shot and the exp valve is probably stuck.

Post your year/model in the future as there are significant differences in the AC from year to year.

SteveG

Just to be sure, we are talking r-12 here.

If they put 38 oz I hope they were just rounding up. I'm not an expert but A/C is the most tricky system and your subpar performance might be caused by overfilling (and charging you how much? or they may have done it correctly and just overcharged you) You don't say if you have rear air, but a car w/rear system takes 37 oz; w/o 33, tops. One oz in a 37 oz system is probably right on, but 7 extra in a car w/o rear might be a problem.

IcemanG17

Mike
Did you do the zip tied trick we did on my car? It worked great on my car.... Assuming the heater valve is closed...& still not cold enough A/C... Did the A/C shop that filled the freon (R12) also check for leaks....without replacing the drier its possible some residual moisture is causing a loss of efficiency? I replaced one leaky hose & the drier....now I consistantly get 50+ degree cooler temps vs ambient (about the same as Bills)...but in order to replace the drier you will loose most of your new coolant (not good)? Good news is a drier is cheap ($25 at specialists...get the parker with sight glass) But Bills machine should be able to remove and reuse your coolant?
Brian

Greg86andahalf

too much oil in system can saturate the expansion valve and diminish cooling.

Very common problem is restricted airflow through the condenser. Check condenser fins for debris, road stones, etc. Look between the condenser and the radiator. You may find leaves, cigarette butts and other bilud-up of airflow robbing stuff. The condenser must be able to cool.

docmirror

Feon is recovered during evacuation. It can be recycled using an R-12 vacuum/pump setup. I don't know the volumes, but too much Freon in the system is bad for it. You can convert to R-134, there's a bunch of posts on this subject. If you stay with R-12, make sure the recirc door is working or you are drawing in hot humid air, and the efficiency is way down.

Doc

Bill Ball

This is R-12. Mike thinks it was evacuated and refilled. No rear AC. I thought 2.5 sounded high too if it was lbs and not 2.5 12 oz cans, although I would expect a shop to go by scales with with a large canister. We can check the pressures, but they must have done that.

He still has some heat coming in despite a new heater valve and checking operation. The center vent was warmer than the door vents. I was able to block off the center vent heat by adjusting the mixer door lever, but it concerns me that hot water is still getting to the heater core. My experience is that the heater valve, as Mickey Mouse as it is, should almost completely block flow. We need to verify that it is closing.

However, even his door vents are not as cold as should be.

It could be the expansion valve, but I'm not familiar with testing it.

His condenser is clean. The whole car is clean.

WallyP

Make sure that the black portion of the heater valve is closer to the head. If the valve is installed backwards, the valve will be pushed off the seat, rather than on the seat, by coolant flow.

And, of course, we are assuming that there is vacuum to close the valve...

surgiblade

First thanks for the useful tips.
Whom would you suggest in the Bay Area to replace a dryer and expansion valve ?
I could not figure out the signature part but I have an 87 928S4 deep blue with white interior.
Spoke with Scott at Devek- tells me takes more than 2 kilobucks to get A.C working sometimes.At this point more than willing to replace dryer and expansion valve- it was 99 degrees today and the A/C simply did not cut it.

Mike

Bill Ball

We were careful about that, especially after seeing one put on backwards on Brian's car. He has vacuum to it and it closes. Srill some heat is present inside the car. More checking and re-checking to do.

GT Jackson

On a side note and not wishing to hi-jack this tread, we did a 2000 mile trip (no rain) and found much water in the left rear footwell. I assume it came from the rear AC which has never happen before.

Question. Does the rear AC cover panel just lift straight off in order to access the rear unit and check the drain or is there something than needs be removed before hand? I prefer not to force it off and damage something.

Many thanks

IcemanG17

Mike
My thoughts are replace the drier and evac-dry your existing coolant... "if" the expansion valve isn't too expensive you might want to replace it at the same time (just as a precaution?). Once you replace the drier (& add the proper amount of oil) then it should improve things. If you want a shop to take a look at it the guy I used (gave you the #) is very good & he has the PET6 and shop manuals (I gave them to him!)

In the meantime try to zip tie trick...its easy and should improve things....even with vaccuum (which you have) the heater valve will leak down and open when the car is off...so if your running around town the A/C will have to overcome the ambient heat and the heater core!
Brian

Greg86andahalf

"even with vaccuum (which you have) the heater valve will leak down and open when the car is off..."

The Black-Blue check-valve (located ner the brake booster) is supposed to prevent this.

BTW, if not done already, make sure the check-valve is not faulty. A common problem is a faulty valve that restricts vacuum, which may prevent the actuators from operating fully, including the heater valve. A defect would be: if you have a vacuum of 16 going in and only 10 or so going to the HVAC. There should be full vacuum through the valve with no drop. When the car is shut off, the valve should prevent vacuum leak-down since it's a one-way device.

Greg

docmirror

This is a problem I still have. I am considering how to repair it, as the accumulator I would get from any supplier is likely as bad as mine. All it takes is a very small split, crack, or pinhole to leakdown after the car is shutoff. I know mine is microscopic, because my cruise works flawlessley. But, when I start up the car everytime, the heater valve has openned, and the car takes time to cool down. I'm considering just wiring the heater valve closed until Nov.

Someone mentioned the cleaning of the fins in the evap unit. This is also a good thing, I did mine while I had the blower out, and used compressed air from the inside to blow backwards, while I used a vacuum with a long tube to reach into the channel and clean the gunk off the evap.

Doc 90GT in resto

Ron_H

Mike:
Devek uses San Carlos Radiator. Not cheap but they know their stuff and are effective. Ask Scott for their number. He is not far off in his estimate of likely costs. 1 1/2 years ago I spent a percentage of that for AC fixes after half assed trys; until a month ago it worked flawlessly. But I have a compressor problem and a controller problem which recently developed and needs to be fixed.

Before my 928, AC in all my other P cars meant opening a window. Now I am spoiled by AC and power everything in this great GT machine. Almost like going through puberty.