A/C time! R12 to R134a conversion, diagnose bad compressor?

[jayton]

Hello,

My 88 LXi has just hit 100k miles, and the A/C went out last summer. I didn't drive the car much then, but I drive it more now. The temperature outside has gotten to the point that a car without A/C is just unacceptable.

These are the tools that I have:
R134a A/C Manifold Set, 3 hoses (red, blue, yellow)
Cans of R134a refrigerant and the tool that injects it in with the gauge and a trigger
R12 to R134a fittings from Pep Boys

It had R12 in it from god knows how long ago before it stopped working. Maybe the compressor is bad and the R12 is all still in there, I do not know. What do I need to do to test if it is a compressor that needs to be replaced, or just a refrigerant leak? Can I read psi for R12 from a manifold made for R134a? Hopefully, all the R12 is all out of there, so that I do not have to take it to a professional shop to extract it out at the same time they extract cash from my wallet.

If the compressor tests to be ok, is it absolutely necessary to change the compressor oil right away when doing the R134a conversion? If so, which one do I need to buy? They have a whole rack of several dozen different kinds of compressor oil at my Autozone, with all different grades.

If the R12 refrigerant is all gone, then I will need to check for leaks and replace hoses and fittings. Is there anything else I could do to fix that?

My experience with A/C up to this point has always been on later cars, all with R134a originally. Each time I just topped off the refrigerant once every two years or so and the A/C always worked great. I know that I got to make sure these two don't mix together, and I have to be careful to not harm the ozone layer or whatever.

Thanks,
jayton

[Blkblurr]

do you know which compreesor type you have? I have the denso in mine and it works well with R134A. Yo uwill need to put an oil stabilizer for R134A into your system to make the old oil compatable with the R134A. You can get it at Adavace Auto etc. If your compressor is not running you can jump the pressure switch for low coolant once you have your gauge set installed and ready to put more coolant in. If the compressor is running already look at the sight glass on the reciever /dryer to see if you have bubbles and freon liquid flowing. If yes to both, you just need to charge the system. Of course you need to recover the R12 if you still have it in your system. If not you should use a vacuum pump to pump down your system and use the gauge set to see if you have a leak in your system after you pump it down.

[Dr_Snooz]

If you haven't lost your R12 already, you will if you do any repairs to the system. Converting to 134 is fairly easy these days and you can buy a kit from Napa pretty cheaply. It comes with good instructions that you should follow carefully. If you have a Keihin compressor, it's the reason your system stopped working. Just throw it away, because it can't be repaired or improved and buy a Nippondenso unit. That's pretty expensive, though, and you might have to swing by the local junkyard for a different compressor mount.

Finding leaks is tricky and I'm not sure the best way to do it. Most shops will pressurize the system with new freon and UV dye, then use a black light to find the dye. I didn't find this very effective, but that's probably because I was using a meager pen-sized black light on a bright July day.

My understanding is that the oil is the big problem in converting. All (or most all) the R12 oil must be removed or neutralized or it will react with the 134 oil. There might be something made since I converted mine that makes this easier, but for me it involved a special solvent (from Napa), an air nozzle and a lot of patience.

I don't think 134 gauges will work on an R12 system. If it were me, I'd just depress one of the Schrader valves slightly to see if there is any pressure in the system. It won't waste much freon and will tell you whether or not you have to take it to a shop to have it removed.

Oh yeah, and you'll need to add a vacuum pump to your list of tools on hand (~$200).

Good luck!

[snoopyloopy]

if you have the conversion kit already, then just put the 134a conversion connectors on the r12 connectors and then you can just use the guage that came with the kit. mine is converted, and probably leaks somewhere. but it's not fast. at any rate. i just refill it when it gets warm.

[Dr_Snooz]

if you have the conversion kit already, then just put the 134a conversion connectors on the r12 connectors and then you can just use the guage that came with the kit.

I think you have to remove the old Schrader valves first, so that probably wouldn't work real well.

['A20A3']

i got a nippondenso compressor and bracket..just removed it all. it works, good shape. suprisingly my A/C worked before i removed it all! haha 3G rarity.

lemme know i dont need this stuff make a decent offer and it's yours. :wave:

[Blkblurr]

The conversion kit I got from Advance Auto came with an oil stabilizer. You just drain the same amount of oil out of the compressor and put the stabilzer in. i used a can of pressurized fluorecing dye added to the freon to find the leak in my system. It was at the manifold that connects the compressor hoses to the condensor core. The o-rings were hard and leaking. I replaced them, evacuated the system for about an hour to dry the moisture out and shut the vacuum pump off, closed the valve on the gauge set and let it set for several hours to see if the pressure climbed. It did not so I found the leak. I then charged the system with R134A to about 85% charge.This is the recommended charge leval for R134A

[Dr_Snooz]

I then charged the system with R134A to about 85% charge.This is the recommended charge leval for R134A

That amounted to just about two cans, right? I did just over two cans, but it might have been too much as it's leaking again.

Doh!

[Blkblurr]

Two twelve oz cans, yes

[jayton]

Awesome responses guys. I will post back with what I have found.

Thanks!

[Oldblueaccord]

http://www.autofrost.com/autodisc.pdf

I have been reading some on this stuff called Autofrost. Seems interesting esp for people who are not having good results with r134a in our cars. I have not used it but ahve used Freeze 12 in a r-12 setup and r134a in my Honda both with great results.



wp

[nswst8]

I use this sight alot for my a/c needs
http://www.aircondition.com/tech/questions/82/Troubleshooting-with-Gauges-FAQ