drb007

I have spent hours searching the previous posts on the ac in a 964. Learned a bit. I had a schroeder valve replaced last spring and the R12 recharged. It worked about as well as I hear everyone say a 964 might. This spring it worked ok, and would cool nicely on the highway, but was not so good in town. Thought it would just need a recharge, or that I might have a slow leak. I took it to a corner "radiator" shop that advertised ac work for a check up. It took them about 10 trys to move the car (kept killing it), and couldn't figure out the difference between the condensor for the ac and the radiator for the oil...
Anyway, they said they pumped out the R12 and I had only .49 lbs, and I need 1.5 lbs. They also said I could not recharge it as I obviously had a leak. As there was no visible leak, it must be coming from the evaporator in the dash (next to the heater core they told me I have...) 6.5 hours plus parts to fix it they say. About $750. No thanks I say.
Well, we can suck out the R12, and put in R134a, just this once. That would only run $200. But it will likely leak out, and I'll still have to do the big job later.
"I'll have to think it over..." Bye.
So now the problem. When I brought it in there, it was cooling, just not enough. Now, it doesn't cool even a little. I think they neglected to put my R12 back in. Possible?
I plan to take it to a different shop this week for a check up. Hopefully they will at least do a leak test and maybe run dye through the system. I am considering getting some R12 and putting it in myself (can I?) or I have heard a bit about Freeze 12...can I do this myself?
Thanks for any advice.

jimq

They cant pump R12 back into a leaking system. I hope they gave you credit for what they took out. That stuff cost a arm and 2 legs! You cant buy it yourself. Read earlier post last week on R134/Freeze12 pros/cons.
i just recharged my own previously converted R134 system and it cost less then $10.

Heirsh

if/when I have trouble with my AC I will order the parts appropriate for a changeover to r134a and then recharge it myself. R12 should work a bit better in a similarly sized system, but at least you dont have to rely on ppl with the licenses for the coolant. There are some previous threads on this. Its only a cpl parts and you can go down to whatever autostore is in your area and buy 134a.

drb007

No, they didn't give me my R12 back, and I didn't get credit for any of it...
So if I convert to R134a, can I do the conversion myself?
Dave

agentpennypacker

yes - you simply buy an "A/C Charging Kit + retrofit R134a". I purchased one not long ago (Advance Auto Parts)for $35 or so - came with 3 cans of R134a. You have to make sure all of the R12 is out (or have whoever takes it out make sure it is all out) before putting the R134a in there. The kit should come with two adaptors for your system (low pressure and high pressure ends). Easy job to do.

jimq

Check out Jaime (Wachuko) replacing evaporater thread in the 964 How to do forum. If they can do it for $750 that might be a good deal. I dont think they know what they are getting into.
You can tell its summer. All the airconditioner problems are resurfacing!

craig001

Well, Porsches were never really known for their AC were they?

I shot some R-12 into my system recently and it only gets down to the high 40's. I may have put oo much in, but I can't find definative numbers anywhere. Is there a seperate Technik publication on the 964's AC system? Also I know from my records book that the Schroeder valves have been replaced twice since the car arrived in the states. I may see if this one shop I use will let me supply my own R-12 when we get back from the Parade.

The other thing to check is the condenser in the left front well and make sure it's clean.

JasonAndreas

A/C system capacities
R12 (1989 - 1992) 930 g (2.05 lb)
R134a (1993 -1994) 840 g (1.85 lb)

Compressor oil:
Densoil (1989 - 1992) 100 +- 20cm3 (3.4 +- 0.7 oz)
ND 8 (1993 - 1994) 140 +- 20cm3 (4.7 +- 0.7 oz)

JasonAndreas

drb007,
There is a TSB (Part Identifier 8770 - Number 9401) for leaking A/C lines. I have no idea (i don't have AC) if the problem relates to yours but basically it says, "Under certain circumstances, refrigerant loss from the area of the expansion valve pipe connections can be misdiagnosed as a defective expansion valve." Basically up until 10/93 Porsche was using bolts that were too small so the expansion valve would distort and cause a leak at the pipe connections on the valve. The fix was to use a M6 x 30mm bolt and only torque it to 10Nm.

craig001

Jason,

Do you happen to know the high and low pressure numbers? I didn't evacuate my system when I shot the Freon in there so I couldn't guess a weight. I've got a 17# tank of the stuff and just shot some in and then read the guages.

JasonAndreas

When checking the refrigerant capacity the pressures vary quite dramatically with temperature, from 0.4bar to 1.3 bar for low and 10 to 21 bar for high pressure. Check your PMs for a "graph". If anyone else needs it just send me a PM.

springer3

There is a reliable quick check to see if your freon charge is about right. If the suction line to the compressor feels cold after driving on a hot day with the AC on, you have plenty of freon. The suction line is the big one. You will burn your hand if you touch the discharge line while the compressor is running.

Don't vent freon if you suspect you added a little too much. You will lose an unknown amount of oil if you vent, and you will be breaking the law. The receiver/dryer contains a surge volume that lets you get away with adding a few ounces too much freon. If you get it too full, you lose the gas cushion for the compressor discharge, That can overload your compressor and cause serious damage.

If the gas is OK and you are not blowing nice and cold, check for dirt/bugs/chaff clogging the condenser fins. Mine was filthy before I cleaned it. Verify the condenser fan runs.

Feel the air from the cabin vents with the thermostat on "cold" and AC compressor turned off. If you feel heated air, that means the mixing flaps or the servos are letting heated air mix with cold air. If all that is fine, perhaps the compressor is tired. Is it original? More than 5 years old? There is a good chance it can't put out pressure like it used to.

My 92 has a relatively new compressor, and a cleaned condenser. I am running R-12. The "angel's breath" from the cabin vents is as cold as the AC in my Mercedes E-class beater. After sitting in the sun all day, the cabin cools off within the first mile or two even in Atlanta heat and humidity. It is a myth that 964s do not have adequate AC systems.