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Zdeno

Question About Expansion Valve

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Hi guys, I bought the A/C compressor 2 days ago and ready to change it by myself or by my mechanic. It will be fourth compressor to this car. Last owner change the system from R12 to R134 what cost him $1600 (included remanu compressor) after 6 month they had to install other compressor under waranty. Now 1,5 years later it is me who will change the compressor again. I bought remanu compressor from Florida with new clutch and receiver/drier. I told this compressor story to woman from who I was buing the compressor and she told me this -

- Hi, Do you happen to know if the shop has ever changed the expansion valve?

that's the part located behind the dash, inside the car. The way they check this part is by the pressure readings they get after charging the system. The job of the valve is to regulate the pressures in the system. And when they go, they can cause to much pressure to the compressor and causes it to overwork. You wont really have any symptoms, until the unit gives out.

My question is - Does anybody know where the expansion valve is and what do you guys think ? is it true about the valve. I didn´t find anything about where the valve is. THANK YOU !! And if can tell me what I NEED TO EXCHANGE WITH NEW COMPRESSOR. It is my nightmare. I´m afraid that I will install new compressor and it works just for a month or two.

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the expansion valve is in the dash with the cooling unit. bottom line if you are so affraid just buy all new parts

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The early LSes had an EPR (evaporator pressure regulator) valve downstream of the evaporator, mounted right against the firewall in the engine compartment.

An EPR is more typically used where multiple evaporators are served by one compressor, many minivans have them. Other than to quieten the expansion valve outlet noise/sound I never got a satisfactory answer from Lexus.

But.

The use of an EPR in this manner allows "unused", liquid, freon into the downstream side of the evaporator. Often evidenced by up to 1/2" of rime icing on the outside of the inlet line to the compressor. Eventually that will lead to liquid refrigerant entering the compressor, a very BAD situation indeed.

If you car has an EPR, 92 does, then I would have that checked immediately.

And by-the-by, unless you are very careful with cleanliness changing the compressor is not a DIY job.

Expansion valves...refrigerant contamination (system has been "opened" three times.....??) might restrict the flow which would not harm the compressor but would reduce the functionality of the system significantly. Having the expansion valve "too" open would result in freezing up the of the moisture on the evaporator core and that would soon result in no airflow to the passenger cabin, no functionality. altogether.

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I replaced the expansion valve in my 93 after the compressor shredded itself and pumped the a/c system full of metallic debris. I also replaced the condensor and receiver/drier at the same time and installed an inline filter in the suction line next to the compressor. I installed a filter from Pace Compressors that has a replaceable filter element and even though I tried to purge and flush the system of all the metallic debris, after 4 filter changes I was still capturing some metallic debris in the filter element. It is quite possible that you have the same situation going on and that is why the compressors are failing. The expansion valve replacement in the 93 is an intimidating job but I actually had the entire under dash unit removed from the car using the instructions in the shop manual in less than an hours time. It is a pretty tight job getting it back in but it is do-able if you have at least average mechanical ability. Since your car was converted it's also possible that the system was not purged of all the mineral oil that was used in the R12 system and that oil is not compatible with the synthetic oil used with the R134A system. Cleanliness and having the proper manifold gages and equipment to service the system with gas is an absolute necessity. If you have a lot of debris in the a/c system that might be clogging the expansion valve, you could actually be drawing a vacuum on the suction input to the compressor. If you are seeing a vacuum at the compressor suction side, that would be an almost sure sign of a bad expansion valve.

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What is the problem with your compressor? It's unusual to just go through compressor like that. What is the reading on Low and High side? You have a leak in your system.

JPI

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I don´t have a leak. Just A/C compressor is blocked. When I turn on the A/C the compressor doesn´t work. Just blocking the V-Belt and the clutch doesn´t go around - Just stay in one place and the belt slide around the clutch.

Obergc - all the things were change 1,5 years ago with compressor. So do you think that I have to change all the things again ? Do think that it won´t be enought to change just compressor + rediever/drier + espansoin valve ??

Thank you guys !

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With the compressor, the receiver/drier, and the expansion valve you have just about everything but the condensor and the hoses/lines. By blocked I assume you mean that the compressor is locked up. If you do have a lot of debris trapped in the condensor, it is hard to flush it out when the system is cold. You can remove the condensor (hard job, you have to remove the whole front bumper) and take it to a shop to have it professionally flushed. At the very least I think you should put a filter in the suction line to trap the debris once it starts moving through the system and keep it from trashing the new compressor. Just my opinion.

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