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2009 Honda CR-V EX-L - good pressure, no fan or compressor when AC "on"

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  • 2009 Honda CR-V EX-L - good pressure, no fan or compressor when AC "on"

    I am troubleshooting niece's 2009 CR-V with the auto climate control. Static pressure is about 100 (at 85 F outside temp). Condenser fan does not engage with AC switch on dash (switch lights up) and neither does the compressor. Swapped relays for compressor and condenser fan - no change. Checked fuses - all good. Question on testing low pressure switch: where is it and how to test three wire pressure switch on a Honda? Parts description says it is three wire. If I apply power at the relay box directly to the output terminal the fan will run and compressor will also run with power jumped - I did not test pressures with compressor jumped. Does low pressure switch "disable" the fan and compressor relays? Will I lose freon charge if I swap out the low pressure switch if it tests bad? Thanks for your help!

  • #2
    Welcome bhap: This transducer/switch may or may not just swap out without losing "refrigerant" is a better word than freon to use still a word used for a brand name product no longer made since '93 just stuck in people's vocabulary.

    Compressor should look like this...…
    Image of Denso A/C Compressor : Part number 471-7056
    The "transducer switch" should look like this...….
    Image of Santech A/C Switch : Part number MT1618
    If you want to play the parts toss that's your call I don't really suggest that rather do some more diagnosing. Compressor will NOT engage for a lot of reasons like most now computer controlled to default to not engage and when it does should put fan(s) on also cool engine or may work for cooling radiator if warm anyway know the difference.

    Static pressure is in line with temp higher because of engine heat only means system is not empty not that it's ready to work.

    Would help if you have a pressure reading with it engaged AYOR jumping things or end up with blowing the ECM (computer that runs this whole show) ever doing that.

    Knock off some easy checks first you at least made it compress or engage if fans didn't also come on probably made a new problem! At that time it should have been able to blow cool air inside if not condenser fans not much or any.

    Fuses should be checked with either voltmeter or test light not just by looks if not done that way check again.

    Another check for this common type compressor is the air gap of the clutch. Almost universal when off should measure .020 or so if no feeler gauge a well folded biz card should be tight or too tight to fit in that gap. If too wide especially hot weather it will not pull in to engage or be intermittent. Most are adjustable and probably has to come out never sure of how much room you have to do that if the problem.

    You could tell with care tapping on it when A/C is requested on outer hub if it snapped on/engaged that's the issue and can dismiss all the rest till that's right.

    Discharge likely for either the switch or taking compressor off if needed.

    If you go this far you want to know how much refrigerant comes out and fill to exact amount no guessing there if you can't do that or get that done properly you are just at high risk to make a lot of things all worse.

    Before this gets to be a total vocational course in automotive A/C make sure your diagnosis is correct and nothing plain obvious is the real problem.

    Should be the first warning that almost anything A/C is not DIY friendly and worse than other things doing something wrong like jumping things already done can cost a fortune.

    An idea that might be best for you is to just pay for the diagnosis then decide if you wish to take this on. Ask what a professional diagnosis would cost up front will save you money, mistakes will just make it worse as said,
    Tom
    MetroWest, Boston

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    • #3
      I concur with Tom, 3 wire "pressure switches" in modern stuff are much more likely to be transducers that are a sensor, with 5+ volt , signal out and ground, and jumping or shorting them can damage electronics.
      At the very least your going to need to get hold of a manual for the system.
      Static pressure is high enough that I don't think it would prevent the system from starting, at least initially but that doesn't mean it is enough to function.
      Even if the system is charged it doesn't necessarily mean the sensor is the problem, That is where the manual can be a help, hopefully it will have a way to test with the sensor in place, it could just as easly be the wireing to and from the sensor or the control board or any other parts of the system.
      On the hopeful side your problem isn't intermittent so the shop doesn't have to wait until it acts up.
      Unless you have access to the factory manuals and testers, I think this is best left to a dealer.

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