A/C Help
 

Hi guys,
My A/C does not blow cold so I added two 14oz cans of R-12 thinking it was low since I have not added Freon in more than 3 years. Still does not blow cold. The compressor runs and the low pressure switch is good so it must have enough charge. The class window on top of the dryer is foamy and the line from the dryer to the dash is ice covered when the A/C is on. I am not an A/C expert so any help will be as always greatly appreciated.

It sounds like your drier is clogged and the high pressure liquids pressure is being redused and the refrigerant boils off after the restriction

Not only is your drier most likely clogged, but you should also replace the expansion valve, particularly if the system has been open for those three years. You will need to replace all o-rings while you're in there...

And, it would be a great opportunity to retrofit the system to 134A.

Is there an expansion valve on a 1984?

With R12 this is typically a sign of an undercharge, but don't add more refrigerant yet.

The liquid refrigerant is changing phase, from a liquid to a gas, before it exits the expansion valve (also called a TXV or TEV). In a normally running system the only condensation or frosting you will see is on the evaporator outlet pipe where it exits the evaporator. What you are observing is related to either:
A) Moisture in the system that is freezing and creating a small aperture large enough to allow the the liquid refrigerant to change phase (liquid to gas), or
B) A partially closed TEV, most likely do to moisture freezing inside it. I would not replace the TEV just yet.

The moisture problem usually happens when the system is not properly evacuated (pulling a vacuum on the system) to remove ambient gases (air) before you put the refrigerant in the system.

Just a suggestion before you spin your wheels tearing things apart.
1) Properly, what you would want to do is as suggested, replace all the o-rings in the system if that has not been done before, the original o-rings would be hard and brittle by this time. Replace the receiver drier because over time the desiccant inside gets saturated with moisture. Fix the leaks before put more refrigerant in the system, the most common leak points are the compressor to condenser hose, the compressor, the condenser to drier hose; tell tale signs of a leak are refrigerant oil a the leak point. Since the system has been leaking refrigerant it probably lost refrigerant oil, how much is always a guess, however if you inject or add 2 to 3 oz of refrigerant oil (you can use Ester type for this scenario) you will be ok.
2) Properly evacuate the system using an ac vacuum pump. Charge the they system with the R12 if you wish using the OEM charge amount (there should be a label in the engine bay noting how much), for a 944 its around 2 lbs or 32 oz.
3) Use a set of service gauges to inspect and monitor the low and high side pressures along with a Pressures and Temperatures chart for the type of refrigerant you are using.

Why, yes there is...

http://forums.pelicanparts.com/uploa...1437309045.jpg


http://forums.pelicanparts.com/uploa...1437309125.jpg


http://forums.pelicanparts.com/uploa...1437309153.jpg

I searched Pelican for the valve and they carry one for 1985.5 and newer 944s, also the A/C parts diagram/illustration page showing the complete A/C system does not show one either. Anyway is the valve as shown in the first 2 pictures, located at foot well on driver side? What is the one by the condenser on last picture? You can tell I am a novice on A/C. Thanks for the help to all that replied I truly appreciate it.
PS: Your quote "944 constant tinkering" is so true.

I posted the three pics so you would have an idea of what's involved with replacing the expansion valve. The last pic shows the valve (center front). The early cars utilize a different expansion valve and it took me a while to find the correct unit. Vertex Auto in Miami usually keeps them in stock but they're over $100.00 so be prepared.

..and a spare is handy JIK

http://forums.pelicanparts.com/uploa...1437337066.jpg

http://forums.pelicanparts.com/uploa...1437337099.jpg

J_AZ

944.573.201.00 if you are sticking with R12

Thanks, Yes I am sticking with R12.

kuehl/griffiths is the man for Porsche AC stuff....under the VW number 477-820-909-00

Just a thought... I switched to 134A for several reasons:

1. The car can go to most any shop as R12 is getting harder to find, especially if you're on a road trip.
2. R12 is pretty nasty for the environment (this is actually my main reason for switching freon type).
3. My AC works so well that I don't even use the highest blower speed.
4. I get positive comments when people see the 134A retrofit sticker under the hood (ok, not so much...).

BTW: JohnAZ sent me his AC repair tutorial a couple years ago which really helped me out when I performed major AC surgery. Thanks again John as she's running great, even in this 90+ heat.

What's involved to change over to 134? I'm assuming I don't have to crawl under there and remove the entire unit as shown in the pics. Maybe I shouldn't assume!!!

Read:
A/C R134a Retrofitting

You probably will still need to remove the AC unit from under the dash to change the "O" rings.

Use ester oil-it mixes better with old AC compressor oil.

J_AZ

Thanx. Sounds simple enuff. How difficult is it to remove that unit from under the dash? No need to clean out the hoses or evaporator? I ask because I just want a nice driving 944,but it seems the ones I look at say the compressor works but does not blow cold. I suppose it could be from sitting without gas and the o rings have dried out. Expansion valve bad. Drier no longer working. I don't really know. I do know that AC is mandatory where I live. 105 yesterday. I just don't want to buy a car and immediately have to start tearing it down for days.

Westy, your symptoms are derived from charging a system without pulling it into a vacuum. Moisture from ambient air cannot be condensed. It raises the systems operating pressure, clogs the drier (makes sense?) and you lose all efficiency.

The expansion device has two failure points. One, the inlet screen can become clogged. Secondly, the valve is opened by a rise in pressure in the sealed sensing bulb and power head assembly, which is an entirely separate hermetic system which is not effected unless the transmission line becomes damaged or rubbed through. Both issues cause the same symptom- they starve the evaporator.

That being said, replacing the expansion device may not be necessary in this instance. If you replace the drier, evacuate the system with a proper vacuum pump and recharge you should be OK. Retrofitting to 134a, replacing the expansion device, oil and O-rings is a great idea for overhauling the AC system, but it sounds like your are looking for a more immediate solution.

Westy,

It's not difficult, just take your time and remember what goes where. There are a few electrical connections, vacuum hoses, as well as the freon lines (high & low side). This will also give you the opportunity to clean out the ducts, hoses, etc.

Bradical,,,,,,,thanx for responding. In short, I don't need an immediate solution, I just want to do it right the first time. I don't even mind replacing parts that still work but have a history or propensity to fail. Especially if I need to start tearing things out. Wife and I have two trips coming up, so truth be told, I wouldn't get much summer driving in, and fall would be a great time to do the work as it's cooler in the old barn.

I'm kind of putting the cart before the horse here, as I don't even have a car yet. But I DO want to know what I'm in for so I can be prepared and informed when the right car comes along. I've learned in the past, if ur not ready to pull the trigger, the good ones always get away.

I have half a tank of R12, but that's pretty much reserved for the Z. I have 10 cans of R134, so it just makes sense to be able to convert any existing system that I end up with.

EDIT- This information is for the early 944 & the 924S


Unit under dash is easy to remove.
After the glove box and kick plate are removed, take a picture of the wires and hoses---makes it easy to finish.

Here is the "Quick Version"
Evaporator unit removal on early 944 - Rennlist Discussion Forums

http://forums.pelicanparts.com/uploa...1437502937.jpg

Here is the kit you need or similar:

http://forums.pelicanparts.com/uploa...1437502911.gif

J_AZ