iloveporsches

Ok, when I bought the car at the end of last summer, I knew the AC didn't work. I figured I'd just get it fixed over the winter no problem. Well, a clutch job and head rebuild later, it isn't fixed. Now having to drive a black/black car in 90*+ with no AC is really starting to suck. The AC blows on all settings, but it just blows warm air.

Is this just a recharge, or could it be a lot more? What's a recharge of R12 or a convresion to R-134a cost?

HY M8NC

A re-charge is probable. That usually means a leak in the system.

These cars have a safety switch that will not allow the compressor to come on if it is low on refrigerant. The refrigerant carries the oil in a modern A/C system.

There are conversion kits for sale-I think Interdynamics makes one-although I've never used one. Some people on the list swear by them. Check the archives-there have been a lot of posts on this subject.

qoncept944

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by iloveporsches:
<strong>Well, a clutch job and head rebuild later, it isn't fixed. Now having to drive a black/black car in 90*+ with no AC is really starting to suck.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">You and I are so alike..

I'll assume you checked the fuses already. It's possible it just needs recharged, and your best bet in that situation would be to convert to R-134a and recharge it yourself with a kit from Autozone or whatever. A R12 recharge'll cost you a fortune, period.

But I kind of doubt that's the case. My guess is if you do need a recharge, it's because you've got a leak, but more likely yet is either the compressor or the compressor clutch. Watch the compressor while you have a friend turn it off and on, if it engages -- well, the clutch isn't bad and I'm lost, but if it doesn't, you likely just need to clean the grounds to the clutch or replace it. A rebuild clutch on ebay costs about the same as a whole compressor, so you'd be in the same puzzling situation as me.

Also, my dad's friend told me straight up, "You don't want to try to fix it yourself. Take it somewhere."

Who knows.

qoncept944

BTW, can ANYONE tell me how much R-134a I'm likely to need to recharge the system? I realize you aren't going to be able to tell me exactly, but give me something to ponder, please. Say it's completely discharged, is 1 of those cans from Autozone going to fill it? Will it take 10? Assuming there's no leaks, of course.

HY M8NC

My little capacity chart lists 944-89-91 (don't ask why it is only those years-I have no idea), uses...
33.44 ounces of R-12, and 2.7 ounces of mineral oil. My brain seems to think that the correct "re-calculation" to R-134a is 80% (26.75 oz) of the refrigerant, but 2.7 ounces of PAG oil. The 134a refrigerant works at a higher pressure. At any rate, this is a starting point. To tell if the system is in full charge, the inlet and outlet of the evaporator should be within 5 degrees of each other. If the outlet is warmer-it's overcharged, if the inlet is warmer-it's undercharged. Get a friend with a temperature probe, or a laser thermometer. Keep in mind that the "1 pound can" at an auto parts store is 12oz, not 16oz.

RobbyK

I hate to hijack this post but when I bought my car the guy said he changed the system over to R-134a but never had it charged(Seems like bull but hey judging by the way work was done on this car it might be true) is there a way I can tell if it was really done and what is it going to cost to charge to R-134a?

RobbyK

bump

craig001

If you system was converted there is usually a sticker put near the valve by your drivers dide strut tower. In older 944's this is the low pressure (suction) side. One newer 944's Porsche made a change and the top valve (read easily accessable) is the high pressure side. The low pressure port is down right off the compressor kind of hidden by the alternator cold air pipe. You have to access it from underneath the car which is a PITA. Also there should be adapters on the valves to alow the use of R-134a. Do a search through the threads or on the web and there are charts out there, but I can't remember the specific sites. Hope this helps.

Also, Porsche designed the hoses to leak a little so that in a overpressure situation the thing won't blow up. So just because you need freon doesn't mean you have a bad leak. It could just be a time issue. You can buy AC Leak dye that you use with a black light to find leaks. Or take it to a shop. They can leak test and then draw the system down for a couple of hours with a vacuum and refill with your choice of R-12 or R-134a. Remember that to convert the system you should replace the receiver/dryer, o-rings, and drain the oil out of the compressor and replace it with PAG. You may be able to find a lubricant that is compatible with both R-134a and an R-12 system. R-12 uses mineral oil and the R-134a uses an ester base which shouldn't be mixed. Someone will correct me if I am mistaken about this.

There is also AC system sealer for either system but I have no experience with that product.

RussRPJ

There is a good comparison between R12 and R134a at the Griffiths website.

I had a couple of related questions. Had an AC tech working freelance put 134a into my empty system back in early May. I have no idea whether or not he replaced the mineral oil with the ester base. I really doubt it. Plus, I still have the stock receiver/dryer in place. So, what can happen with mixing R134a and mineral oil? Why would I need a new receiver/dryer? Looked over the system under black light (my R134a has the dye incorporated), no leak found. Had to replace the infamous broken AC rod clip this weekend, and it runs nice and cold now. I need to know what to expect. Thanks.

HY M8NC

My limited knowledge says that the reason you need to change oils is that mineral oil will not be carried by the 134a. The two chemicals don't technically mix, but the oil is suspended in the freon. Worst case scenario, the compressor locks. I don't really know if you are in danger of that, or what. Anyone else?

Peckster

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">
[QB].

Also, Porsche designed the hoses to leak a little so that in a overpressure situation the thing won't blow up.

QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I find this hard to believe. A slow leak won't prevent anything from blowing up, and is damaging to the environment. If you have a leak in an R12 system you should get it fixed.

I just had mine converted last week for about C$350 all in, it works great now. You can't get R12 in Canada anymore.

There were conversion kits on Ebay last week, you might want to contact the seller. The auction was <a href="http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33548&item=2421078464" target="_blank">http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33548&item=2421078464</a>

RussRPJ

Hmmm....yeah, R12 is getting a bit rare lately. Shops don't even like to admit they have it on hand. I had thought about pulling the 134a out and going back to R12 just for piece of mind, but what an expensive aggravation that would be. Like I say, so far so good with the oil and vinegar mix. But the future?

Pressure in my system is 30 psi on the low side, right at 200 on the high. This is what was recommended for the 134a. A slow leak is a slow leak. To engineer a built-in fault doesn't make sense. If it were that dangerous, porsche would have put in a pressure relief valve!

craig001

Here's the blurb from the Griffiths Site:

AC HOSE LINES

What are Barrier hoses: Imagine a hose within a hose. Barrier hose has an additional liner that greatly reduces refrigerant loss through the hose walls. And if you are wondering about those little pin holes you see evenly spaced on the outside of the hose, they are there for a reason: in the event that the inner lining fails the refrigerant will be safely released through the outer wall as opposed to building up pressure and exploding the case. Barrier was introduced as OEM equipment in the early to mid 90's with the mandate to use R134a refrigerant. All Griffiths hose assemblies use certified barrier hose.

The URL is <a href="http://www.griffiths.com/porsche/ac/" target="_blank">Griffiths</a>.

Peckster

Here's something else they say that's interesting.

"The a/c hose lines on the 924 and 944 were made of traditional hose (rubber). This original type of hose was designed during the time period when R12 refrigerant was inexpensive and it's affect on the ozone level was not known. This old fashion hose line slowly leaks (permeates) refrigerant through it's skin overtime. It was common to "top off" or recharge the system on a yearly basis. Today, with the high cost of R12 it's not wise to have leaks of any kind."

gleamingred944

There have been lots of threads on R12 vs. R134a. Search for them.

Basically, all the connectors are supposed to be different in a converted system and an a/c specialist knows which is which. If you convert, you lose about 1/3 of cooling capacity because the Porsche evaporator was not designed for R134a. If you have leaks, R134a will find them much faster than R12 does.

I converted - really wish I hadn't. I needed to replace all the fittings, the drier, then had leaks that needed a leak-sealing additive to stop. Cost me $400 Cdn for parts alone.

Mind you, it works now!