hp1480

Thats very interesting ,this is what happened .My compressor& clutch failed after 8 years and 105832 miles.I was in Montreal at the time and had Lexus replace compressor with a new one .In May 2002 after 15832 miles the compressor was dying and so was the evaporator .I replaced the compressor with a remanufactered Lexus part (Lexus gave me the replacement at no charge )and the evaporator,an expansion valve was also put in ,the O rings were replaced and receiver assembly .Now 5 years later and after 33498 miles ,I'm faced with needing another compressor & clutch .The one thing that may bear out this so called moron mechanic is ,on freon the AC lasted 105000 miles .On 134a 15000 & 33000 miles.

There is an unusual design aspect of the '92 LS400's A/C system that even your (even were it true) "highly regarded" mechanic might be unaware. It has an EPR valve upstream of the evaporator core. These are more commonly used to "meter" the high side liquid refrigerant when two or more separate evaporators are used on one compressor/condensor system. Without the EPR one evaporator could potentially HOG all of the cooling capacity. Front/rear A/C setups in minivans for instance. I have come to believe that Lexus used the EPR to lessen the noise factor "HISS" that you might otherwise get with 200 psi pressure differential between the liquid and gas side, across the input and output of the expansion valve. The Lexus EPR valve, even during "normal" operation can/will often allow refrigerant cooling capacity to exist beyond the evaporator core, and into the refrigerant return lines to the suction side of the evaporator. After a long period of operation on a humid day I often see 1/4 of rime ice accummulated on these return lines. So, should the EPR valve be maladusted (it has a "back-pressure" adjustment) or fail in a way that causes liquid refrigerant to reach the compressor inlet, the compressor life will be shortened substantially, due to something called compressor "slugging".

I thank you for your good advise .It didnt seem logical although the compressor that is failing was a retrofitted one so I could use 134a instead of R12.

Agreed, seconded. I'll 3rd that. I think you need to drop the "highly regarded" from his title. Compressors are designed to run on R134a. When a conversion is done it's important to get all of the r12 out of the system since the 2 refrigerants are not compatible. Also important to use the right kind and amount of compressor oil. I also replaced all the o-rings when i did mine. May have been overkill but many recommend it. I suspect that there was something missed on your original conversion to R134. Check out Tech Choice Parts, or AC Parts Now. I bought AC parts from both places and was happy with prices and service. Then find another reputable mechanic.

I own a 92 LS400 .In 2002 I replaced the whole airconditioning (compressor,clutch,evaprorator etc)went from R12 to R134a fluid.Now my compressor is failing again ,and I talked to this highly regarded mechanic about replacing the compressor with an aftermarket unit.He said that he could do that but would only do it if I agreed to go back to R12 fluid.He claimed that the replacement unit that was able to use R134 was shortening the life of the unit ,even though it would work with R134 ,I would be better off going back to R12.Is he correct in that ,or is he misinformed .

My Lexus dealer has diagnosed that the ac light flickering is the compressor clutch is binding .Usually I can turn off the ac and turn back on ,and it will work.My question ,is there anyway to stop the clutch binding and free it up.This is a 92 LS400 ,and I want to keep it for a while .I replaced the whole original ac 8 years ago and remembered it cost over $5000.Any suggestions?