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Thread: A/C temperature cycling switch question 1993 minivan

  1. #1
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    A/C temperature cycling switch question 1993 minivan

    Trying to figure out some info on how the a/c is controlled on a 93 minivan. There is a temperature cycling switch mounted on the expansion valve. It looks like the one here:
    https://www.rockauto.com/catalog/mor...nid=527&jpid=1

    I was assuming this switch cycles the clutch off when the refrigerant leaving the evaporator is at a certain temp (probably near freezing) BUT, i don't know for sure.
    Does anyone know what temperature the switch operates at? Or, is this just a temperature sensor that the ECU uses to switch off the clutch?
    I was hoping it could be used as a live switch in the a/c clutch circuit to open at a certain temp.

    Thanks for any assistance.
    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
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    '89 Plymouth Acclaim 2.5L turbo auto, "Slugmobile" yes, THE Slugmobile!
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  2. #2
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: A/C temperature cycling switch question 1993 minivan

    Anyone got any info?
    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
    '05 PT GT 2.4T HO autostick (RIP)
    '89 Plymouth Acclaim 2.5L turbo auto, "Slugmobile" yes, THE Slugmobile!
    '89 Dodge Caravan SE 2.5L turbo auto, "Mean Mini" yes, Gus' Mean Mini! (Current best 11.699 @ 114.43 mph! - Oct 15th, 2022 Cecil County Dragway, MD)
    MeanMini dragracing videos: https://www.youtube.com/playlist?lis...URZLB1RxGYF6vw
    and other cars, trucks and motorcycles
    https://www.youtube.com/user/SlugmobileMeanMini

  3. #3
    Hybrid booster
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    Re: A/C temperature cycling switch question 1993 minivan

    You could pull the switch ( or a replacement ) and see what temp it switches to open. The old chrysler stuff ( 73ish ) works the same way a cooling fan temp switch works except backwards.
    A/C temp switch = normally closed to allow current across, gets too cold, opens and no more compressor clutch.
    Rad temp switch = normally open ( no fan ) gets too hot, closes to allow current to flow to the fan motor.
    The a/c temp switch on the duster almost looks like the adjustable temp switch for the electric rad fan.
    It's just a temp probe with an internal set temp, very simple and they don't fail very often.
    I was looking over the pinouts for the ecu and it only has an A/C clutch sense pin. The ecu needs to know that the A/C is on but doesn't look like it controls the A/C clutch.
    Last edited by player1up; 03-04-2016 at 10:48 AM.

  4. #4
    turbo addict
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    Re: A/C temperature cycling switch question 1993 minivan

    I know on my 91 ram the cycling switch cuts off the compressor when the evaporator outlet is near freezing. It does all of the clutch switching on my truck but it is a larger unit and has a relay built in.
    Ian Adams Function>Form 1990 shadow scrapped, too rusty:( 1991 Spirit R/T Scrapped, parts sold:( 1989 Turbo Caravan Daily beater with built-[I]ish [/I]​engine slowly evolving into weekend turbo beater.

  5. #5
    turbo addict
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    Re: A/C temperature cycling switch question 1993 minivan

    This is the diagram for it. looks like this unit just interrupts the circuit inline from the low pressure switch to the ECM. So to the ECM it just cycles the low pressure cutoff.
    Attached Files Attached Files
    Ian Adams Function>Form 1990 shadow scrapped, too rusty:( 1991 Spirit R/T Scrapped, parts sold:( 1989 Turbo Caravan Daily beater with built-[I]ish [/I]​engine slowly evolving into weekend turbo beater.

  6. #6
    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: A/C temperature cycling switch question 1993 minivan

    That's kind of what I thought it would do, just interrupt the clutch curcuit if the evaporator temp got too low which could mean the evaporator was freezing over. But, i took the switch to work and tried to test the switching temp, but couldn't generate a temperature below freezing in the instrument shop. I could have taken it into one of the freezers and checked with a meter i guess, but that wouldn't tell me what temp it switched at.

    Ian, on the pdf i have a hard time reading the text. The middle wire I think is labeled white, does that say it comes from a fuse? Does it say which fuse number and amp rating? I have the wiring diagrams for a 93 minivan with 2.5 4cyl and a/c, but i don't remember that. I'd have to see if I can find them.
    Wayne H.

    '91 Dodge Spirit ES 2.5L turbo 5spd
    '05 PT GT 2.4T HO autostick (RIP)
    '89 Plymouth Acclaim 2.5L turbo auto, "Slugmobile" yes, THE Slugmobile!
    '89 Dodge Caravan SE 2.5L turbo auto, "Mean Mini" yes, Gus' Mean Mini! (Current best 11.699 @ 114.43 mph! - Oct 15th, 2022 Cecil County Dragway, MD)
    MeanMini dragracing videos: https://www.youtube.com/playlist?lis...URZLB1RxGYF6vw
    and other cars, trucks and motorcycles
    https://www.youtube.com/user/SlugmobileMeanMini

  7. #7
    turbo addict
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    Re: A/C temperature cycling switch question 1993 minivan

    I can check later but I think its fuse 8.
    Ian Adams Function>Form 1990 shadow scrapped, too rusty:( 1991 Spirit R/T Scrapped, parts sold:( 1989 Turbo Caravan Daily beater with built-[I]ish [/I]​engine slowly evolving into weekend turbo beater.

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