I am helping a relative to get the A/C to work again. It is '92 Accord. The A/C has not been used in the last 10 yrs. There is no air coming out on the high side and low side valves when pressed. It appears that the R-12 refrigerant is completely gone. The heating is working normal during winter time.

We would like to convert it to R-134a. What should I check or replace in the cooling system before recharging it? Thanks in advance for any advice.

 

I'm no AC expert, but I would simply buy the inexpensive R12 to R134a conversion kit and charge it up. You could buy some of the r134a that has the UV dye in it to try to see if it is leaking from anywhere. Sure, the r12 had to have leaked out somehow, but when you say the AC hasn't been used in 10 years that does not surprise me.
You may want to wait for some AC expert opinions first though. (There are several members on here who are)
I just wanted to put in my $0.02 - whether it is worth anything or not.

 

I don't know what needs replaced to convert from r12 to r134a, but I am sure that TexasHonda knows that answer.

You should get a manifold gauge to make sure that your a/c system is charged, and you will need it later when evacuating and recharging the system. It sounds like all of the freon is gone though.

There must have been a leak somewhere. Freon evaporates quickly, but the refrigerant oil will remain and collect dust. Look over the entire system (behind the a/c pulley, at any junction). The shaft seal on compressor is another common place for a leak.

 

I too an no A/c expert, but I am in the process of fixing mine as well. My neighbor is a mechanic and gave me a few tips. He suggested I pump the system with some air (<60 psi) to find the leak. He said nitrogen is preferred to minimize the chance of water condensing in the system if you don't have an air drier on your compressor. I had to splice an air fitting into an a/c hose that I bought at autozone for $10. Then just listen for the air bleeding out (I had a bad low-side valve stem). It has been holding pressure for a few weeks so I think I am good. The next step is to use a vacuum to draw out all the air (leave it run for at least 20 min.) Then just buy a 134a conversion kit from an autoparts store and pump it up. the kit I bought came with the conversion fittings, a hose and gauge, and a few cans of 134a and oil. Good luck!

 

Thanks for all the suggestions/tips. I will inspect the car to see any sign of leaks in the system and then do some steps as you suggested.

guinnessmike - Did you replace the low-side valve stem? If so, how did you do that? It looks to me that the valve stem in my relative's car is irreplaceable.

 

Check ackits.com for acparts you may need. Good shop for parts and good forum (www.autoacforum.com) for questions.

For best performance, I would pull the evaporator and clean. Replace all orings on expansion valve and temp feedback sensor w/ new orings lubed w/ Nylog or equivalent. Drain evaporator of any lubricant. You may want to consider a new expansion valve designed for R134a. They are fairly inexpensive and will improve performance.

Replace all orings in connections.

Check both hoses for indications of leaks (oil/dirt). If suspect, replace them.

Inspect compressor for indications of lubricant loss around rotating shaft (big oil/dirty ring in the plane of the clutch assy). If you see an oily, dirty ring replace shaft seal or replace compressor w/ new, used, or rebuilt. Shaft seal is easy to replace once compressor is removed. Install 3 oz of oil (Double End PAG or Polyester oil) in comprressor after draining completely. I have found used compressors to be a great bargain, < $50 vs. $200+ for rebuilt which may not perform as well.

Blow air through condensor and tubing sections to flush most lubricant.

Last thing before closing system is to replace receiver/drier and add 3 oz of lubricant.

Replace R12 fittings w/ R134 adapters (good quality from ackits, not Interdynamics)

Connect vacuum pump through manifold gauge set and pull as much vacuum as possible. Close manifold valves and monitor vacuum. It should hold almost steady, but might drop slightly and stablize. If it goes to zero, you have a leak that must be fixed.

If add about 25-27 oz of R134a to system. You might start w/ two, 12 oz cans and see if system is cooling good. If Ok, leave it alone. If not adequate, say temps> 50F then add 2 oz at time till vent temps max out, then stop.

Check AC w/ doors/windows closed, max fan, recirculate and 1500 rpm engine speed. Park car in shade. System should stablize w/i 5-10 mins and produce coolest temps after about 20 secs of compressor running.

A converted system may not perform as well as system designed for R134a, but I would expect you can get 45F temps and cool the car adequately.

Let us know what you decide and results.

good luck

 

Initial inspection of the hoses and fittings didn't see any sign of leaks in the systems under the hood. I haven't checked the evaporator yet. When I turn on the A/C, the clutch is not spinning, and the air coming out is not cold.

TexasHonda - Thank you for giving such detailed informative instruction in checking A/D components step by step. I will look at the link you provided and do the steps you suggested in this upcoming holiday break.

 

Since system has zero pressure from your first post, then a leak exists somewhere.

It may be worth investing in a professional leak inspection. They introduce R134 and pressurized nitrogen to push system pressure up to perhaps 100-200 psia and check for leaks w/ a sensitive electronic refrigerant detector. Once leak sites are known you can repair yourself.

If you do a conscientious job of repairing and rebuilding, you can achieve an effective AC system.

good luck

 

When the pressure is zero, the low-pressure safety switch prevents the AC clutch from operating, to avoid destroying the compressor.