Calling 993 a/c experts

[Rick Lee]

Well, after 14 yrs. of ice cold, flawless a/c, it's finally having issues. I can't believe it's lasted this long, never once been serviced. It still blows very cool, but no longer ice cold. This just started an hour ago and it's a good 112 deg. out today. How do I diagnose this? I don't want to pay for a recharge and then find out my evaporator is bad or that I have leaks. What's the process for tracking this down?

[lucittm]

Rick,
If you have had good performance from your AC for 14 years, do a happy dance. That AC system owes you nothing at this point.

You likely have a slow leak at one of the many o-rings in the system. They dryout, shrink over the winter, or just crack from old age (ozone?).

If you are running R-134 as a refrigerant, then you can do this yourself. Buy a recharge kit/hose and some replacement R-134 from a reputable shop, you don't want the recycled stuff. And also buy a can of dye. It should come in a smaller can, maybe 4 oz. Put the dye in first and then recharge the R-134.

You should notice an immediate improvement and hopefully a leak somewhere you can actually see. Most of the dyes show up better under a blacklight (UV) but most can be seen in regular light. If the leak is obvious, you know what to do. Maybe just an o-ring.

Otherwise the leak could be in the condenser or the evaporator coils. If that is the case, you may want to live with it and recharge a can or so of R-134 each year because it gets expensive to have a technician find the leak, rip out the offending part, and purchase a replacement.

Good Luck,
Mark

[Rick Lee]

Man, I am such a know-nothing when it comes to a/c stuff. Did Porsche use R-134 or R-12 on these cars? How much does R-134 run these days? How many cans will I need?

[e3photo]

993's have R134 in them, and probably have a sticker on your compressor confirming this. I have just been thru this and will be replacing my evaporator and drier.
I bought a can of freon with UV dye in it, and a $10 UV penlight at the auto store.

I charged up the system and let it run a few minutes, then in the dark of the garage I looked at everything with the light.

If you take the pollen filters out, you can see the evaporator, and on top of it is the expansion valve.

If you take the liner out of the front left fender, you can see the drier and condenser.

I had everything apart, and looked at all the connections with the UV light.

Just saw you over at Rennlist. Follow along.

Emerald

[Lil bastard]

While you can do this yourself, it won't be the best job.

Pros, at least the good ones, don't use dye anymore, they use a 'Sniffer', an electronic detector which can pick up the leaking gas in parts per million; a leak so small the dye won't penetrate it for days.

Also, the system really needs to be made tight prior to recharging the refrigerant or you're just gonna lose it to atmosphere in little time.

And, for the system, esp. the receiver/drier to be fully efficient, it needs to be evacuated using a vacuum pump. This lowers the vapor pressure in the system so the remaining gas and old oil (which is now mildly acidic) literally boils off.

They will then add the precise amount (by weight) of oil and refrigerant to max out efficiency at the vent. The improper amount of either of these will result in less cooling and could actually lead to early death of the compressor - mucho dinero.

Considering AZ spends weeks or months at 100+ and the fact that amortized over the past 14 yrs., the expense isn't that great, if done properly, there's no reason you won't get another 10-14 yrs. out of it.

Cheers!

[LUFTMAN]

install dye and run for a while then raise car up and see if you see dye running out of evaporator drain these models are know for evaporator leaks sorry tom

[kuehl]

Originally Posted by Rick Lee

Well, after 14 yrs. of ice cold, flawless a/c, it's finally having issues. I can't believe it's lasted this long, never once been serviced. It still blows very cool, but no longer ice cold. This just started an hour ago and it's a good 112 deg. out today. How do I diagnose this? I don't want to pay for a recharge and then find out my evaporator is bad or that I have leaks. What's the process for tracking this down?

If its 101F outside and dry vs. 112F outside and humid, you will notice a difference in cooling performance.

For the moment, assuming you don't have a refrigerant leak, a sudden loss in performance could be:
1) Evaporator core is freezing; moisture between the cooling fins has turned to ice. A test would be to turn the system off for 20 minutes or so, let it defrost (you would notice water dripping out the condensation drain tubes under the car), turn it back on and if things get to 'normal' again then your car may have had a freeze.
2) Condenser fan motor is not running at max speed, its running on its low speed or no speed rather than full speed.
3) A flap or actuator that regulates mixing outside air or heated air with AC air is not fully closed.

If you are suspecting a refrigerant leak you would have a tech attach a set of gauges to the system and check the systems pressures; this is the most cost effective method if you consider what your time is worth, maybe the shop might charge you say $25. to $50 depending upon how busy they are. Or have the system evacuated and recharged with refrigerant, refrigerant oil with a tracer dye, and then 'sniffed' with an electronic leak detector (common points of leakage on your model are evaporator, expansion valve, compressor, hoses in the engine compartment, possibly condenser if there is debris collected at its base). Refrigerant o-rings can fail however not often as they are static seals not exposed to the outside and the minor surface that sees refrigerant is covered with refrigerant oil as the system operates.

[Rick Lee]

Maybe I was just being a hypochondriac. Friday night I got in the car to go to dinner and the a/c blew as cold as it's ever blown. I figured it would act up again along the 20 mile trip, but it did not. And it was ice cold again on the way home. I sort of look forward to diving into this job, if it's really necessary. But I'd like to put it off until it's a little more comfortable to work in the garage. I will have a shop check the pressures though.

[kuehl]

Buy an inexpensive digital thermometer if you want something objective to compare in your notes. Here were your temps for Friday:

Temperature: High 106.2 °F low 88.6 °F
Humidity: High 37% 36% Low

If you are going to 'compare' vent cockpit temps you need same outside side temps or your not apples for apples.

Write it all down.