how can i bypass the air conditioning low refrigerant pressure switch?

Posted by fanatic26, Jun 15, 2008
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  1. fanatic26

    fanatic26 Proven Member

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    Patterson, California
    On my 1996 GST I have a functional A/C system with a bad pressure switch on the top of the compressor. This was verified by a mechanic as we charged the system and he ran some kind of a bypass blowing ice cold air. My question is, how can I do this myself? I had the system leak tested and filled and I know its full. I just want to bypass the bad switch for now.
    #1
  2. diggerzmound

    diggerzmound Proven Member

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    looking at the schematic, the pressure switch is a dual pressure switch. With only two wires it has to be going to ground, so grounding both wires should bypass.
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  3. JusMX141

    JusMX141 Moderator

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    You can make a simple jumper wire to jump across the two pins on the pigtail.

    This technique is normally only used to make the compressor run initially to draw freon into the system when the system has been completely drained. You should NOT drive your car around with the low pressure switch bypassed; the freon carries the oil throughout the system. If you force the compressor to run when there's too little freon in the system, the compressor will not get proper lubrication and fail.

    If you suspect the low pressure switch to be bad, REPLACE IT. You do not have to drain most systems to replace the switch.
    #3
  4. BlackdOutGST

    BlackdOutGST Proven Member

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    Found zero other post that helped with this problem. When I turn on the A/C in the car, the compressor clutch kicks in and out, nonstop. Suspected Low R134, charged and still have the problem. Next suspect, Pressure cycling switch, O'reillys computer doesn't show the car to have one. Anyone have an idea?
    thanks
    #4
  5. pj91gsx

    pj91gsx Freelancer

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    push in the valve on the ac line to see if it has air in it. I have a switch on my ac line. you may have a leak in the ac lines and not know it.
    #5
  6. Fastass96

    Fastass96 Proven Member

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    It turns on and off when it is low recharge it to 45psi.
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  7. Defiant

    Defiant DSM Wiseman

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    glorious Galt, California
    It isn't the switch. It's the AC control unit. Mitsubishi has stopped supplying them.
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  8. diggerzmound

    diggerzmound Proven Member

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    Broken Bow, Nebraska

    Wonderful............... :notgood:

    I think I read another post that described this as a little control box in the passenger kick panel.. Is this correct??
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  9. JusMX141

    JusMX141 Moderator

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    The low-pressure system must be near the 45psi mark for the compressor to run constantly. You also MUST have the "recirc" option chosen over "fresh" on the dash lever.

    Recently I was having a similar issue with my father's '98 Caravan. The compressor it uses is identical to a DSM compressor (the van has the Mitsu 3.0 V6). I absolutely could NOT get the compressor to stay running constant with 45psi on the low side. Last week, the compressor took a dump on him.
    #9
  10. BlackdOutGST

    BlackdOutGST Proven Member

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    I am pretty sure there are no leaks, because when I attempted to recharge it, it was already almost overcharged.
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  11. JusMX141

    JusMX141 Moderator

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    Be advised that the pressure must not exceed 45psi on the low side as well, or the system will also shut down.
    #11
  12. BlackdOutGST

    BlackdOutGST Proven Member

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    Ok, I can't remember. To check the charge on the A/C system.
    I hooked up gauge turned the motor on and the A/C on. Is this the correct combination?
    #12
  13. BlackdOutGST

    BlackdOutGST Proven Member

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    Nevermind, I got desperate and released some pressure out of the high side with the motor running and A/C on, the compressor stopped kicking in and out after I released a good amount of r134. Conclusion = Overcharging the system is not hard to do. Still scratching head because it had these symptoms before I overcharged it. Anywho! It work now.


    Note* Recovery of r134 was done by EPA certified technician.
    #13
  14. awdtalontsi1992

    awdtalontsi1992 Proven Member

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    I'm also having some problems with my 98 Talon GS's A/C System. The compressor isn't kicking on. I've checked and the refrigerant level is good. I jumped the compressor clutch and it is working ok. I jumped the 2 wires on the dual pressure switch to ground as described in a post above. I even jumped the switch in the dash. The only time the compressor will kick on is if I jump it to 12v then it kicks on and everything works ok but it won't come on by itself.

    I read above about a automatic compressor controller. Do these controllers come on the 2.0L Non-turbo Talons? If so, where is it located in the car and is there a way to test it?
    #14
  15. nate379

    nate379 Proven Member

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    Maybe on the low side, but you should be measuring on the high side and it needs to be about 2x ambient temp in pressure with the engine at high idle. So if it's 80* out, it should be around 160 psi.

    Need a guage like this:

    R134 AC MANIFOLD GAUGES HOSES AIR VACUUM PUMP R12/22 :eBay Motors (item 190312925243 end time Jun-13-09 14:48:44 PDT)

    #15

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