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A/C madness

OK guys, it's time for me to show my ignorance. . .

I brought in my car to look at the A/C system (out of freon - nothing in the sight glass & no cold air) summer is coming so I want it to work properly. The mechanic leak-checked the system with the flourescent dye stuff and told me that the compressor and "evaporator suction" hose were leaking (they'd be happy to fix it for $2,000). I said thanks but no thanks, shopped around some and got a rebuilt compressor for $150 (leak tested) and two evaporator hoses (one from compressor to evaporator and the one from evaporator to condensor (I think)) for about $100 (new!) and a new receiver / drier unit, so I saved a ton on parts.

I want to put all this stuff on in a week or two, but I've NEVER dealt with an A/C system. In fact, I've only ever owned one car in my life that had A/C and I never had to do anything with it, so it's a system that I'm totally unfamiliar with. First off - when the guy said the "evaporator suction" hose, he was talking about the one from the compressor to the evaporator right? That one looks like a pain to replace, but I'm sure I can do it with enough time & patience. I bought both evaporator hoses since I wasn't 100% sure which one he was talking about & figured if one was bad, the other was probably ready to go bad anyway. I got the receiver / drier because I've read that without freon in the system they rot out and get ruined (not terribly expensive anyway - $50 for new).

What's the deal with oil in the compressor? Do I need to add oil to it or something before I install it or just bolt the sucker on with the hoses & receiver and take it into a shop to be leak tested & charged? Will they (should they) add oil to it? How much oil do I (or they) add? Is there a way to tell if there's already oil in the compressor? Any do-it-yourself guidance would be appreciated as I'd love to avoid a bill for $1000 of labor I could do myself, I just want to only have to do it once. Thanks!
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Old 02-20-2004, 05:32 AM
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Early or late 85? If early then your low side (charge) port should be on the compressor itself. I'd get a R12 to 134a fitting first and put it on the new compressor. You may need a shorter alt, compressor, crank belt but I'm not sure. Bolt it up, connect the lines, vacuum the system down and see if it holds. My buddy did my charging and put pag oil and 134 in. The capacity of our system is roughly 2lbs, figure in that you'll want about 80% of that if you go with 134. I want to say he put in 8oz. of oil, but I forget. I did not replace any seals or the drier, and it works just fine (47-43 vent temps)
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Old 02-20-2004, 07:14 AM
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Yea this is an early 85 system with the schraeder valve on the compressor itself. I've seen elsewhere on this board that the stock system can handle R134a (I guess it runs at a higher pressure or something than R12), if this is the case, why would I need a 134a conversion kit (other than the different valve size) like the multi-component kits that go for upwards of $500?

Is it really safe to just pump r134a into it?
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Old 02-20-2004, 08:42 AM
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Some will say you need the kit and o-rings, drier, etc.., I say you don't. Vacuum the sytem completely. You will want to have a shorter belt even if you do stick with R-12, it makes it a lot easier to charge.
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Last edited by mattdavis11; 02-20-2004 at 10:27 AM..
Old 02-20-2004, 10:22 AM
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The reason those kits are for sale is because on most other cars you do need a retrofit kit, so the hype about them spilled over into 944's.
There is no reason why (so long as the proper oil is used) an OEM 944 compressor cannot handle r134A. Just remember to fill to 80% capacity, and it will be fine. However, if the compressor is aftermarket, there are no guarantees it will take the pressure.
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Old 02-20-2004, 04:54 PM
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What's the advantage to r134a besides I can do the charging myself? I was told that R12 is okay environmentally so long as it is charged / discharged with the proper equipment (like at a shop) so none gets in the atmosphere. I suppose 134a is cheaper too, right?
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Old 02-20-2004, 06:23 PM
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Bingo!! Cheaper by a long shot, that and you need an A/C cert. to buy R12, even then it's very pricey. 134 doesn't cool as well as R12, but I can live with average vent temps near 45 degrees. This is in central Texas, in a black, non-tinted 944.
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Last edited by mattdavis11; 02-20-2004 at 07:14 PM..
Old 02-20-2004, 07:12 PM
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Yeah, up here R12 is about $150/kg or something stupid like that, R134A is like $20/kg I think.
Technically yes, R12 is harmless so long as it is fully contained and properly disposed of.
HOWEVER, if it ever leaks it is not harmless, not by a long shot, it is also very carcinogenic (or so I hear), plus, another big thing is it's the manufacturing of it that produces many CFC's. That is why it is no longer produced (at least in north america), so the prices will only continue to rise until it is all gone.

I as well would rather pay $110/kg less and live with 5 degree (celcius) warmer vents.
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Old 02-20-2004, 10:17 PM
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If there's no negative implications to the o-rings & so on I'll go with r134a - anybody have horror stories to report?
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Old 02-21-2004, 08:07 AM
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You had better have the proper amount of oil in the system. And the oils are different for R134 and R12. I replaced compressors on two vehicles last summer. The instructions are quite clear about the oil. Mine came with no oil.

If you switch from R12 to R134, you should purge the system of old lubricant.

I use neither R134 or R12. It costs me about $12 to recharge. Been using the other variety of refrigerants for 7 years with no problems on my oldest Mercedes and my 951. The compressors were replace as each was the original compressor that came with the car. Actually, the clutch went out on both compressors. I tried to replace clutch on 951 and screwed up the compressor seal doing the job. I have a Sanden conversion on it now working great I might add. Rather than replacing the clutch on my oldest MB, I just got a rebuilt compressor complete with clutch.
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Old 02-21-2004, 08:52 AM
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PAG OIL!!! No matter what they might say about ester oil, and 134a, use pag oil, please. No problems here. Vacuum out the system.
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Old 02-21-2004, 09:21 AM
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What's the best way to do that? Just take it in once everything is hooked up and say "vaccum it then fill it?"

I don't know jack about a/c systems, but I'm learning. . .
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Old 02-21-2004, 12:01 PM
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Pretty much.
They should always flush/vacuum the system before they fill.
You can hook everything up yourself before you bring it in, and they should clear it and fill it for you.
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Old 02-21-2004, 05:54 PM
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Awesome. Once that's done I'll get one of those 134a kits for $20 and keep a couple cans around for any follow up charges that should be needed but given the amount of stuff that's being replaced, I seriously doubt it should leak at all for quite a while, if ever.

Next question - the compressor looks easy, the compressor-to-evaporator hose (I believe the mechanic called it the "evaporator suction" hose) looks like a monumental pain in the a$$. Any tips/tricks/suggestions?
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Old 02-21-2004, 09:19 PM
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However, chargine the system with 134 will result in higher temps than with R-12. The condensor in your car is not designed for 134 so it leaves it "hotter" than R12.

To do the job right, you should replace the compressor, dryer, and leaking hoses, and the expansion valve. After which, you should have a leak free system.

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Old 02-22-2004, 06:07 AM
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OK, I have the first of the 3 components (see the first post) but not the expansion valve. What / where is it? How much to replace in terms of cost & work?
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Old 02-22-2004, 12:46 PM
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