Question about 2000 Toyota Sienna

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2000 Toyota Sienna. Does it have a low pressure switch? A/C Compressor clutch not engaging. 5A fuse ok and dash A/C light lights. System has some pressure. How do I identify the clutch wire to engauge it to check clitch operation, then pressures? Connector on front of compressor appears to have 3 wires.

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  • noskosteve Jun 23, 2011

    The dash light was coming on when the AC was turned on, but no clutch, thus no cold.
    There is a tripple pressure switch. It has an LP number in MPa (mega Pascal) that, when converted to PSI, is about 29 psi (I don't remember the other two numbers but think they were *very*roughly MP Medium)=150 PSI and HP (High) = 450 PSI. Something like that.)
    The Low pressure switch sends a signal to the main compurer to not engage the clutch, so you need to charge on the low pressure port to bring the static pressure up above 29 psi before the clutch will engage in the first place. A can can do this. Engine on or off makes no difference. Then charge normally. ... MAKE SURE TO BLEED ANY HOSES OF AIR COMPLETELY!
    Mine has a 'sight glass' and a local friend and trained in this said to fill till the glass stops bubbling and no more that 1-2 ounser after that. This "should" be as good as charging to the recommended pressures - which I have been unable to find on-line.
    __IF_ the dash light in the A/C Button does not come on it *may* be the 5 amp fuse (the owner manual only calls several fuses AC, so this is a guess that it is the clutch fuse) This is the one that is really hard to get to on the left lower dash behind and to the left of the small mini-door that I keep a few fuses in. You can NOT reach it by removing that little door! Unfortunately it requires removing the left dash lower panel and that is an extra super royal pain! --- Especially when all you find is that the fuse is good ! !
    That said, and I'm guessing again, the front two fans are another matter and may be fuses or fan motors, but with two out, I'd guess eithera fuse or something else in the computer chain. You need to know that on these cars, just about everything is run by the computer. A guy in the neighborhood recently retired from teaching automotive at the county college and calls it "mother may I". You push any button and the computer actually runs what ever - windows, AC, heater, Lights, etc.
    Good luck.



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The Sienna has had problems with the relay that controls the clutch going bad. Under the hood, next to the battery, there is a fuse and relay box. One will be marked magnetic clutch or an abbreviation of that. If the part number is 90987-02022, it should be changed out to the updated relay with a part number of 90987-02028. It 's around $70 from Toyota or you could find an aftermarket one for about $17 at your local automotive parts store. On some models the a/c light will blink if this is the case but not on all. You could swap it with the fog or possibly the horn relay to see if this is the problem.

Posted on Jun 07, 2011

  • noskosteve Jun 07, 2011

    Sorry. Didn't answer my question. Hunted around and I found that the tri-pressure switch has LP, MP, HP numbers. I converted the MPa values to psi, then when measuring the static pressure discovered it was only 20 psi, below the 29 LP. Then, two cans of R134 and all is in order.
    Regards, Steve

  • tly9 Jun 23, 2011

    You said that A/C Compressor clutch not engaging. Can you still charge r134 when it is still not engaged? Can you explain your steps on how you get the Compressor running and charging? My 2000 Sienna A/C Compressor does not turn and the 2 front Fans also do not turn. I want to buy the R134 Can and charge it to the low side port but I am concerned about how to get the Compressor to turn while doing the charge. Please help. Thanks.



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