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Toyota Repair/Toyota AC


QUESTION: I have a 94 Toyota pickup with the same problem as the guy with the Avalon:  The AC will stop working for no apparent reason. This has happened many time over the years, and when you live in Florida, it gets quite uncomfortable with no AC. Typical scenario: You drive to the grocery store and the AC works fine. An hour later for the ride home, you can't get any cold air. The AC will also stop working while you are sitting at a light. My mechanic, who advertises AC repair, has replaced every part of the system at least once over the years, always for freon leaks. He once mentioned that there was a solenoid that might have something to do with this problem, but he has never specifically looked to solve this problem. I got tired of going to him for AC repair because the freon always leaked out after a few months. I finally serviced the system myself with a can of AC Pro freon with leak sealer and that seems to have fixed the leaking, but still have the intermittent problem. The little control board that sits on top of the blower I have replaced twice myself as well. This thing  reads information from a number of sensors, and has an adjustment knob on it which I believe has something to do with rpm but I don't know how to adjust it.

ANSWER: That control knob is for setting at what idle speed the compressor engages and turns off, it's basically trial and error, turn it all the way one way and then the other and watch the result,
as soon as the clutch engages the idle will go up as long as the compressor is running.

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QUESTION: Okay, that answers my question about the knob.  Any idea which sensor may tell the compressor not to run when I am not getting any cold air?  If I knew where the bad signal was coming from I could fix a sensor or maybe bypass it.

There is a pressure switch on the high pressure line it has a connector with two wires on it bypassing it will cause the compressor to run all the time but doing this doesn't take care of the real problem, other than that the compressor is controlled by engine rpm and line pressures so if the line pressures are incorrect due to a restriction or low pressure the compressor will shut off to protect the system, this can be caused by a bad expansion valve, receiver drier, condenser and evaporator, another reason for the compressor to turn off is engine overheating.

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Ted Ritter


I have more than 28 years experience as toyota technician, I will be able to answer most questions related to the Toyota product line up to the present year models,I am located in the US but welcome questions from other regions of the world. When asking a question please provide specific information: year,model, engine,transmission information. Provide as much information as possible including a brief repair history if possible. I have been a volunteer here for more ten years an have answered over 16,000 questions helping Toyota owners with their problems and save thousands of dollars without any compensation, some of my answers are published on many other websites including google and various automotive forums. DONATIONS ARE VERY MUCH APPRECIATED, IF YOU HAVE RECIEVED HELPFUL INFORMATION PLEASE MAKE A DONATION. AS OF TODAY (JULY 22, 2014) ALL REQUESTED GRAPHICS, ILLUSTRATIONS, DIAGRAMS, PHOTOS, WILL REQUIRE THE MINUMUM DONATION UP FRONT.


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