924Board.org

[neophite]

I cannot fiqure out the problem with the ac in my 87 924S. First i got a new compressor and had the system retrofitted for 134a.After about a week of working fine, I would cut in on and the compressor wouldn't kick in.After 2 or 3 tries it would work. Once the compressor started working sometimes it would quit after about 30 minutes.I could cut it off and back on and most of the time it would kick in again.Eventually the compressor would not kick in at all.I have recharged it, changed the switch which that cuts in on, and the low pressure switch.Same thing. Took it to the shop and they replaced the high side port and recharged it.Worked good for a day or two but slowly the compressor quit kicking in.Any suggestions?

[Grenadiers]

I'd go to parts store, buy a 25 dollar can of R134a with a gauge on it; or, buy a separate cheap gauge. Pump refrigerant in the system, note the amount on gauge. Drive car with a/c on, when it acts up again, plug in the gauge once again, note refrigerant amount. If it changes, ya know you have a leak in the system. A fairly cheap DIY diagnostic test to eliminate the obvious.

As Ideola Dan said awhile ago, the R12 hoses are different than the R134a hoses. As a former Carrier hvac parts person, we sold vacuum hoses/gauge a/c test packages for the different refrigerants. You could have a leaky hose, but that wouldn't happen as quickly as you reported. My former '87 had the R134a switcheroo, and held a charge for the summer only.
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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

[ideola]

Definitely sounds like a leak, which is causing the low pressure switch to turn off the system. During a retrofit, ALL of the old oil must be evacuated, and ALL of the seals must be replaced, as the newer style oil will eat old seals (from what I've read). Are you sure everything for the entire system was retrofitted? If they didn't do the stuff in the evaporator plenum, your leak could be up there. Also, it is highly recommended to replace the receiver/dryer/accumulator during a retrofit. You didn't mention that, was it done as well?
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erstwhile owner of just about every 924 variant ever made

[gohim]

Don't waste your money on the R134a can with the low pressure gauge built onto it. They things are so inaccurate, and unreliable that they are not worth the time to figure out where to try connecting to your car.

Spend the money (less than $50 fromt Harbor Freight) that it would cost to buy a proper ac manifold gauge set and a cheap voltmeter. You need these tools at the minimum to get a handle on what is happening in your ac system.

The ac manifold gauge set is used to see what is happening in both sides of the ac system (low and high) at the same time when the ac system is off and when it's turned on. The gauge set is also used to fill the system with refrigerant and for vacuum testing after the system is opened. The voltmeter is used to see what the high and low pessure switches as well as the ac clutch coil are doing.

The compressor oils used with R134a are different from the oil used with R12. That's why a proper conversion includes the flushing of the ac system to remove all of the R12 oil. The Receiver/Drier/Accumulator filter media contains much of the oil in the system, and can become gummed up or clogged when you change refrigerants. that's why you are supposed to replace it when changing refrigerants. The hoses that were used with R12 are too porous to be used with R134a, as R134a particles are smaller than R12 particles, and can leak through the hose material. Earlier R12 seals are not compatible with R134a, and can deteriorate when exposed to R13a compressor coils. The R134a particles can also leak right by the R12 seals.

Why did the shop that did the repair after the conversion change the high pressure port fittings? Was the R134a conversion fitting leaking, or did whoever did the conversion fail to replace the R12 fitting with a R134a fitting (fittings for each type of approved refrigerant gas are different, and when changing refrigerant gasses, the high and low port fitting must be replaced or coversion fiting for the gas being installed must be installed for a LEGAL CONVERSION).

If the person/shop failed to install the correct fittings, I higly doubt if the conversion was correctly done.

[neophite]

I sincerely appreciate all the replies.The shop replaced the seal in the high pressure port.I know absolutely nothing about ac and therefore do not know if the retrofitting was correctly done.However, when I tried to recharge the system with 134a I had to buy an adapter for the fitting which I quess means it was not changed.I did try to recharge the system one time when it quit and the gauge on the can indicated one time that it had adequate gas and another time that there was a problem in the system.I think I will order a set of gauges and try the fiqure it out.Thanks again for your help.

[ideola]

My bet is an incomplete or incorrectly executed conversion. Something to be said for Doing It Right The First Time.
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erstwhile owner of just about every 924 variant ever made