A/C. Nothing's simple on these cars is it?

[alfadoc]

My black on black S2 has non-functional A/C. It's been in the mid 90's here and really humid, and this is my daily driver. I need A/C.

Silly me, I assumed that the system was simply empty, and settled on Envirosafe 12a and their leak stop. Interestingly, the folks at Envirosafe recommend NOT pumping the system into a vacuum, as it makes the HC based refrigerant behave as if the system is overcharged.

Anyway, the stuff arrives today. Yippee. I get my gauges out, install the R12/134a adapters, hook up the can and no clutch engagement. Hmmm. OK, so we'll jump the low pressure switch at the receiver/drier, and...nothing. What the heck? OK, let's hook a long jumper wire from the positive battery terminal directly to the wire going to the compressor clutch and...nothing.

So I guess there's a break in the winding for the clutch electromagnet. Been working on cars since the 1970's, a good bit of that time professionally. This is a first for me. I am not a happy Porsche owner. Anyone have a spare A/C clutch kicking around?

Venting mode off.

[stogie25]

See if there is a spec racing group in your area. They strip these cars and are usually happy to get rid of the leftover parts.

[John_AZ]

alfadoc,

I know that it can be frustrating to work on the AC and I also had my clutch coil connections break off on coil. The replacement is easy. I got an ebay used compressor with clutch/coil and swapped it.

You have experience from the '70s.

I have heard of Enviro-Safe as well as a lot of other non EPA SNAP approved replacements. Why would you not use R134a while it is still cheap and available? AC shops will not work on replacements that will comtaminate the equipment.

Wal-Mart at about $10 a can. I retro fitted my '87 and 2 years later I can still get vent temps in the very low 30s.

Enviro-Safe FAQ - Is it legal to use Enviro-Safe™ Refrigerant in automotive applications?
or
Print Page - AC not cooling that well and need R12

Here is a file to help you with the compressor:
http://home.comcast.net/~chwilka/images/190E/ACCompressor/acpump.pdf
OR
1988 911 Nippondenso A/C Compressor Rebuild

GL
John

[billy mild]

Is it worth it to try a used compressor out or just go straight for the rebuild?

[Jrboulder]

I've got a compressor off an 86 turbo. The clutch is all yours for the price of shipping. Ive got WAY too much of this junk sitting around.

I'm running r134a. Very cold.

Jackson

[John_AZ]

Originally Posted by billy mild

Is it worth it to try a used compressor out or just go straight for the rebuild?

You would need to put new seals in a used compressor. The front shaft seal usually will be bad. A shop may charge $75 to do the work or you could DIY with parts. ( and experience). More if races need replacing.

Porsche Nippondenso Compressor 10P15 Seal Kit compressor seals, nippondenso, denso, seal kits, air conditioning compressor seals, 10p15c seal kits, 10p15e seal kits, 924s seals, 944 seals, 911 seals, 930 seals, 911 compressor seal kits, 930 compresso

GL
John

[SolReaver]

Consider rebuilding your old compressor while you have it out and clean the system. Apply Vacuum. If it holds for a few hours.... Put in pure 134A. No stop leak or dyes. Some advocate replacing all the seals. I do not. Most of the seals are OK to get to, but others, especially the AC core seals are a mother. Replace the seals that leak and whatever you take apart. consider replacing the dryer if you can get one reasonably priced.

[Porsche-O-Phile]

As someone who has done an extensive amount of fighting with the a/c systems on these cars, I would strongly advise against just shoveling refrigerant into the system and/or just replacing a compressor. Here's why:

The most common source of failures of the a/c system is a loss of oil, resulting in a compressor internal failure. The most common reason for a loss of oil is a system leak. Let's look at what often happens:

A small system leak (which is not uncommon due to o-ring degradation or vibration/pulling on one or more connections in the system) causes the system to lose refrigerant+oil. The owner typically remains blissfully unaware of this until the day the a/c stops working, usually because the pressure switch refuses to allow the compressor clutch to engage. This pressure switch is there for a reason - it detects that there is insufficient pressure in the system which means not enough refrigerant plus oil circulating in the a/c refrigerant loop to adequately lubricate the compressor internal parts. By preventing the clutch from engaging, it protects the compressor from running with insufficient lubrication. It's doing its job protecting the compressor.

So anyway the frustrated owner 9 times out of 10 goes down to AutoZone or WalMart and buys a can of refrigerant and throws it in. This allows enough pressure to build in the system to satisfy the pressure switch, which allows the compressor clutch to engage and the system begins blowing cold air again. The 944 owner at this point usually feels very satisfied with him or her self and goes on their way, not realizing the damage they've just done (at this point I won't even discuss the idiots that say "screw that stupid pressure switch and simply jumper it to +12V, defeating the entire purpose - yes folks, they're out there...)

All too often they've replaced "X" ounces of lost refrigerant in the system with "X" ounces of new refrigerant. The part they're failing to consider is that the "X" ounces that was lost originally was REFRIGERANT PLUS OIL, not just refrigerant. If they replace it with just refrigerant, they've diluted the quantity of oil in the system to possibly harmful levels. If this cycle repeats several times (leaks don't usually fix themselves) it isn't long before there is virtually no oil in the system and only refrigerant, which has hardly any lubricating benefit to the compressor.

Usually it isn't long before the compressor goes "kablammo" internally as a result of this, which sends little particles of metal and other contaminants into the far-flung recesses of the evaporator, expansion valve and everywhere else.

The 944 owner goes "what a stupid POS car this is - the compressor is shot, I'll just replace it". So they go out and buy a cheapo compressor off of Ebay and bolt it up, fill the system with refrigerant (hopefully with oil) and think all is well. Of course they haven't fixed the leak, so they end up repeating the process and grenading the "new" compressor. Of course the little metal bits floating around the system aren't helping either.

At this point the 944 owner says "what an a-hole, that guy on Ebay ripped me off - I'm buying a NEW compressor". So they go order a nice shiny new Sanden or Nippondenso unit, bolt THAT up, carefully fill the system with refrigerant (plus oil this time - they've learned from their mistake!) and think all is well once again.

A few weeks later the new compressor siezes too. They forgot to flush out the system and get rid of all the crap from the previous two grenaded compressors that's making mincemeat of the new compressor internals, regardless of proper oiling. Of course the system is still leaking but hey...

And so it goes.

The moral of the story is, to properly fix an a/c system, FLUSH IT thoroughly. THEN pull a vacuum on it to ensure there are no contaminants or moisture in it. Put the new compressor on and fill the system with refrigerant PLUS OIL plus a leak detecting dye. Find any leaks (check the connections at the evaporator - hint, hint) and if any are found, STOP, discharge the system (recover refrigerant - it's cheap enough to have this done), FIX the leak (replace the o-rings ya cheap bastid), THEN refill the system with refrigerant PLUS OIL.

NOW your system will be fixed and reliable and you shouldn't have to resort to carrying around those silly recharge cans.

If you're putting a can of recharge refrigerant into your car, IT HAS A LEAK! Don't deny it, fix it! If you absolutely, positively MUST use one of those things and can't fix the system properly for a few weeks or whatever make sure to buy one of the ones that has the proper type of oil pre-mixed into it. And don't mix refrigerant types (r134a or r12). But I'll say it again - if you're adding refrigerant to your a/c system, IT HAS A LEAK! It should be fixed PROPERLY (ya cheap bastid!) as soon as possible.

It's not that hard to do this but as the above example shows, it's easy to make very expensive and frustrating mistakes and extra work for yourself if you don't think things through properly. Don't skimp, don't get lazy and don't get cheap. You CAN get the a/c system on a 944 working properly without too much expense or heartache if you put the effort in and do it correctly. Hint - "doing it correctly" is NOT shoveling cans of refrigerant from Wal Mart into the system.

Good luck, stay cool.

[Porsche-O-Phile]

Corollary to the above: For anyone looking to buy a new car (well a "new to them" car, especialy a 944), be wary of sellers who say things like "a/c needs to be charged" or "a/c needs a recharge" or "a/c worked fine a while ago then stopped working".

All of these mean THE SYSTEM LEAKS and will need to be fixed per the above steps.

A word to the wise should be sufficient. In and of itself a leaky a/c system is not a reason to pass on a good deal, but be aware that some effort will be required to get the system working right and not eat compressors as quickly as tanks of gas.

[billy mild]

See my A/C worked great last summer and previously. At sometime it started to leak I'm assuming. Well I tried to recharge it and got no where. It would run for a minute get cold then stop.

I took it to a shop they looked at it and found out the clutch slips when hot. So I am currently not driving the car. They recharged the system and it worked the other day, but I know I need to replace the compressor with a used good one or use a rebuilt one. The one on ebay looks like a good deal. So I may just end up doing that.

[SolReaver]

POP: Yes, you will need oil...that usually comes with the compressor rebuild. Make sure you have the right amount of the right oil for the right refrigerant or it turns into ick. This IS an important point so thanks for the input. Cleaning out all the old (usually nasty) oil and junk is really important and so is leak testing. I find that at this late date, ALL the compressors I run into pretty much need rebuilding and you really can't clean and flush a system properly with the compressor in the loop. If you are going to spend the time to clean the system properly, you might as well put a rebuilt compressor on there. Otherwise you might have to go back in when the old seals fail. I don't enjoy AC work so I want to do it once and do it right. My guy rebuilds em for about a hundred dollars and does a good job. he also tests the unit and the peace of mind is worth the money for me. You can rebuild em yourself, but I let someone else do it as he has built thousands. IF the system is holding vac for a while...chances are good that you won't be leaking and hence you won't be wasting R134. Take your time and make sure the mating surfaces are clean and the seals are good. lubricate the seals with the correct oil and install them carefully.

Stop leak and dye are for sissies. Real men use the straight stuff.

Oh, and be careful transporting and installing the new pump with the new oil...Tilting and angling can spill out a bit.

[alfadoc]

Some interesting points. I will take Jrboulder up on his extremely generous offer of a clutch, rebuild the compressor, flush the system out, evacuate and convert to 134a. I hope I get the same kind of vent temps you do John; I'll believe it when I see it.

Maybe I'll save the Envirosafe for the 560 SEL. I have to charge it once a year, and used the last of my R12 in it last month. Or maybe it's time to convert that one too.

Was the R12 REALLY so horrible? It's a far more efficient refrigerant than 134a. I think the whole thing is a load of bull. Speaking of which, we all know that cow emissions (methane) have far more impact on greenhouse gasses than automotive air conditioners. I wonder how far off bovine emission collection devices are?

[John_AZ]

Well..........................believe it.

This is my '98 Cherokee that I topped of this year with a half can of R134a and the other half went in the '87 924S. Both had similiar vent temps at 68* ambient morning temp a couple months ago.



GL
John

[SolReaver]

My AC blows cold as well. The 134 is fine as long as everything else is up to standards. I was running R12 until the compressor failed and the difference is small. Is R12 THAT bad environmentally? It is bad enough that I have R12 removed professionally. What happens from there...Who knows? but, I do my part. 134 is no big deal if it escapes. AC systems leak and vent all the time and there are lots of cars on the road. Some people believe adding refrigerant is just part of A/C maintenance.

1 plastic bottle improperly discarded doesn't make a big difference....Millions of people agree.

The big difference is in price nowadays. If you have to recharge or reseal your system (and you might have to) you can do it without getting reamed financially. Plus, you get those nifty stickers and shiny new fittings! Birdies smile at you and the Sierra club stops sending you hate mail.

So what about cows....Swampland releases more methane than that! Yea, it is crazy regulation...But, the phase out makes sense and R134 is OK.

I heard that there may be a new standard of refrigerant and that 134 will be phased out. I am doing an AC service now on a car...Perhaps I can get ahead of the curve for once.

[Aufgeladen944]

Well my car is giving me issues. The system has pressure, and has refrigerant (I put in the refrigerant with oil and stop leak three years ago with no problems.) Yes, it had a leak. But it didn't leak again after that so I'm assuming whatever the leak was it was small.

Anyways, my compressor isn't turning on. It was working in April, but now I get nothing. The light on the switch isn't turning on. I replaced the A/C relay (in the fuse box), because that tested bad. Much to my chagrin (and $60 later), the relay didn't fix the problem-still no compressor engagement.

What's my next step here? I have to have air-con. I'm a windows up kinda guy when it gets above 75 degrees

[aj951]

I would start at the compressor and work backwards. With the AC switch engaged, jumper the low pressure switch just long enough to see if the compressor clutch engages. If it engages, you have a low charge and still have a leak. If the clutch does not engage, jumper a wire from 12v directly to the clutch coil to see if it engages. If the clutch does not engage, you have a bad clutch coil. If the clutch does engage, it's something further up the system, like the climate control or bad AC switch. Don't trust the light in the AC switch, it could have just burned out.

A.J.

[alfadoc]

BTW, can anyone share a compelling reason not to use a replacement receiver/dryer? The OE Denso one is rather pricey, and aftermarket ones are not. If I'm gonna go through and rebuild the compressor etc, then I'm definitely going to replace the receiver/dryer.

[aj951]

I used an aftermarket dryer with no major issues. Only issue was the outer diameter was just smaller than OEM and I had to wrap the dryer with some tape to get it to snug up in the dryer clamp.

A.J.

[SolReaver]

I re-used my old dryer and it worked fine. Just be sure to flush it. I have used generic dryers and they are fine as well. Your car...Your call.

Aufgeladen944: Hook up a manifold and jump the pump to check high and low side pressures. IMHO stop leak is evil and should be avoided.

[djnolan]

I don't recommend tape. The dryer on my explorer had an insulator band around it and it rusted thru. Tape may cause the same thing.