Low pressure AC switch???

Discussion in '2nd Gen - 2003 - 2006' started by johnboneske, Jul 13, 2019.

  1. johnboneske

    johnboneske Full Access Members

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    Where is the low pressure cut off on my 03 Expy? I assume its on the accumulator/dryer? Is that mounted behind the ECM on the firewall?( I uploaded a pic, it's it behind it?

    AC has started to have intermittent issues, now it won't run at all. Static pressure low side is around 120, didn't check high side nor have I crawled under it to check for power at the compressor. I was "assuming" the low pressure switch went bad?

    For about last week when I first start it, it doesn't cool at all. After its warmed up(engine) for about 10 minutes, I can shut it off and restart it and then it runs. Today, it won't run at all no matter what I do. Also, I was thinking it could be the gap in the clutch being to big, and when it is warm when things expand it runs then...

    Again, I haven't crawled under it or delved into it to deep yet, but any pointers in where to look first would be appreciated!

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  2. stamp11127

    stamp11127 Super Moderator Staff Member

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    It will be in the low pressure line somewhere between the evap and compressor. Of course Ford is going to stick it in the worse place.
    Depending on what the ambient temp was when you took the static pressure reading, 120 may be way too high.
     
  3. johnboneske

    johnboneske Full Access Members

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    it was about 85° out and I just shut off the engine about 5 minutes prior. I am not against draining the refrigerant and refilling it. I guess it could be over charged?? I tried to bypass the high pressure switch with a wire in between the connector and it didn't engage the compressor.
     
  4. Hamfisted

    Hamfisted Full Access Members

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    Unplug it down at the compressor and check for voltage when you jump the pressure switch leads. You may have some other electrical issue like a fuse or relay, failed clutch coil. It should kick on if you jump those pressure switch leads, unless the PCM is sensing some other issue and won't let the system run.


    Here's a good Youtube video Maku posted that can help...

     
    Last edited: Jul 14, 2019
  5. johnboneske

    johnboneske Full Access Members

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    The pic you posted is the sensor I jumped out, and nothing happened. I am assuming that is the high pressure switch(since its near the high side connector),

    If I jump that connection, it should energize the clutch on the compressor correct?

    In case it matters i have the dual zone automatic digital controls for my Heating/cooling system.
     
  6. Hamfisted

    Hamfisted Full Access Members

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    Do you have any voltage there at the pressure switch harness plug ? Have to slide that little brown lock out about a quarter inch to remove the low pressure switch harness plug from the switch. When I replaced my compressor I must've gotten the harness to compressor plug under too much stress, 'cause the connection loosened up and killed my compressor for a day. I got under there and moved the plugs around to relieve the stress, so hopefully it'll be good for another 15 years now.
     
    Last edited: Aug 2, 2019
  7. johnboneske

    johnboneske Full Access Members

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    I found the low pressure switch behind the ECM(or assume that's what it is), unplugged it, and put a jumper in between the terminals, compressor came right on! So, called all the local auto parts stores and no one can find it?? It may be called a low pressure compressor cut off switch? Anyone know the answer? ​

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  8. stamp11127

    stamp11127 Super Moderator Staff Member

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  9. Hamfisted

    Hamfisted Full Access Members

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    The aftermarket expansion valves don't come with the new switch, I think only the OEM Ford parts do. I had to re-use my old switch with the new expansion valve when I replaced my compressor a few months ago. I forgot about it. There's no schrader valve there, so the freon will be lost. Might be quicker just to order from the link Stamp posted unless the dealer sells it by itself.
     
  10. TobyU

    TobyU Full Access Members

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    I would go to parts store and ask to see "buyers guide"
    Then after you nicely explain to the kid who you have underwear- or at least boots--older than...That its with the antique parts look up books over in the rack on one of the shelves.

    You would like to get the same connector but you could splice a new one etc.....but you have to have one that has same threads or adapt it and that is one more fitting that could leak.

    Start in the ford ac switches section and find one that will work.

    This is if ebay is of no luck. Is that even possible? I have on;y had ONE thing ever I can remember I could not find on ebay on online in the whole world. I know there are a few sitting in a warehouse somewhere and I would have paid a lot more than they sold for. The company that made them changed the design and couldn't help me with any parts info.

    Then you can go to an LKQ of other salvage yard.. That's like a 2-3 part max and you know how to get to it now.
     

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