View Full Version : Revive old AC?

10-25-2010, 06:25 PM
So, I have a 91 GT and while I am fixing my WP leak I want to fix my AC. I assume the compressor is dead from the hose being broken on it and the compressor not coming on when the button is pressed.

So, I plan on replacing/repairing the 2 rubber hoses and compressor for the AC. Is there anything else I should try/check/do?

10-25-2010, 06:50 PM
The compressor wont turn on when there is no pressure in the system, there is switch that cycles the compressor on and off it has to be above a certain pressure and then turns off when at a certain max pressure.

10-25-2010, 07:02 PM
That would explain why it wouldn't turn on :) The bearing sound shot on my old compressor so I am ok with trying to find one to replace it. Just curious if there is anything else in the system I should look at.

10-25-2010, 07:37 PM
Not really. Just make sure it's vacuumed out of all the old freon, and then convert it to r134a. You can do all this yourself if you'd like. Personally, I'd take it to a shop and have them use their equipment to vacuum out the system before you charge it.

10-25-2010, 08:16 PM
Is there crap that can dry and stick in the system? When I got the car one of the hoses was broken off and just laying there. Also, would it be ill advised to just rig up my shop vac to one of the tubes?

10-26-2010, 01:28 AM
They need to get the system sealed and then the AC shop will hook it up to a vacuum pump. This will do two things, pull the crap and moisture out and create a vacuum. After that, you can recharge it. If it's been open for a while, it would be better to take it to a shop and let them service it. It will probably be cheaper in the long run.

10-26-2010, 02:42 AM
Hmm. K, I will look into that. I have never heard of a cheap AC service, but if I replace all the parts first then it may not be too bad.


10-26-2010, 02:59 AM
I always replace the drier and orfice tube with new units when I replace an AC compressor.

Hipster Lawrence
10-27-2010, 03:37 PM
If there is a AC specialty shop in town take it to them. You'll be better off. If you are taking it to a random mechanic you might as well research the subject and do the job yourself.

10-27-2010, 06:45 PM
Not sure. I would much rather buy the needed parts and install then drive it there and have them do the cleaning and recharge. No need to pay labor and inflated parts prices when I can do it myself. Just have them do what I can't.

10-27-2010, 06:51 PM
Here's a quote from a member on alltrac.net.

But I'd have to agree with everyone else, it would probably be easier to just have a shop look at it.

Ok guys, I am a professional AC Tech. I've repaired and charged 100's of automotive AC systems and thousands of residential and commercial AC Units.

The proper method to repair your AC system if it's not doing so well on 13+ year old car .

1.) First flush the system with a flush additive
2.) Recover refrigerant
3.) Remove compressor
4.) Remove Manifold from Compressor
5.) Turn Compressor upside down and use a drill to spin the compressor to drain all the oil out of the system.
6.)Install manifold on compressor with new seals
7.) Pour Appropriate Refrigerant oil into Compressor Usually 3oz is enough
8.) Reinstall Compressor But leave the lines off for now
9.) Replace every O-ring in the entire system with FACTORY TOYOTA O-RINGS!!!!!!
10.)Replace Filter/Drier with new
11.) Use High Pressure Nitrogen to blow any contaminates out of the lines DO NOT USE COMPRESSED AIR, A FIRE or EXPLOSION COULD HAPPEN.
12.)Take Compressor lines and attach them
13.) Fill system with High Pressure Nitrogen to at least 100psi and close gauges and mark the reading on the gauges come back in 15 mins if it's hasn't moved your good, if it has you have a leak.
14.)Discharge all the Nitrogen
15.) hook up vac pump and run vac pump until you reach below 500 microns, preferrable below 250 microns. OR run it for 45 mins if it's a good condition 1.5CFM pump. Make sure all your hoses are tight and sealed before vaccing.
16.) Close valves remove vac pump
17.) Charge system with engine off with liquid refrigerant. So turn the can upside down and shake it.
18.) When the can is felling quite cold and empty close valves and remove can.
19.) start the car, turn AC on MAX and Full blast on the fan.
20.) Finish charging AC with refrigerant. Monitor temperature coming out of the vent. Do not exceed max refrigerant capacity.
21.) Test drive. With R12 after the system has had sufficient time to circulate you should be able to get 34-46 degree air and it should fluctuate as you drive at a constant speed like 55+MPH. It should fluctuate consistantly about 10 degrees so 34-44 degrees it will go back and forth.

With R134a it takes considerably longer to cool down to a acceptable level this does not mean there's something wrong it's just the nature of R134a in a system that is designed for R12. The fluctuations will be the same here about 10 degrees, that is basically the expansion valve opening and closing, doing it's job. Or in technical terms the refrigerant is flashing from a liquid to a vapor in the evaporator.

Also you can buy R12 without a EPA License on ebay. You have to e-mail them telling them you plan to resell it and not use it. It's the legal way of purchasing without a license.. So it's legal to buy without license, but illegal to use without a license.

I get R12 right at my local Napa.

If your AC is not working or recently failed have it checked. When it comes to AC work you really need to do it correctly. It's one of those things in life that you just do right the first time or it'll be hell later.