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Higher Idle with A/C

Discussion in 'Chevy Trucks' started by owen, Aug 31, 2003.

  1. owen

    owen Member
    from florida
    Messages: 34

    85 C20 3+3 454 TH400

    When the air conditioner pump is on, the idle drops pretty low causing the truck to run rough. It doesn't kick the idle up.

    If I turn up the idle with the AC on, then it seems too high when the AC is off and it "diesels" when I turn the motor off.

    What is supposed to make the idle increase when the AC pump is turned on?
     
  2. wyldman

    wyldman Member
    Messages: 3,265

    There is a small electric kicker solenoid on the drivers side front of the carb.It is supposed to come on,and bump the idle up.Check and see if you have 12 volts on the wire at the solenoid when the A\C is on.If you do,the solenoid is bad.
     
  3. owen

    owen Member
    from florida
    Messages: 34

    I found the kicker solenoid, but it looks to be vacuum operated. And you know my problem there :eek:

    The vacuum inlet tube has a cap over it. I have no idea where it is supposed to be hooked to.
     
  4. wyldman

    wyldman Member
    Messages: 3,265

    I've never seen a vacuum operated A\C throttle kicker.You might be looking at a dashpot.Any way you can get a pic of your carb ? Maybe I can get a better idea of what your describing.

    Maybe you have something that is US emission only.A pic would make it much easier.
     
  5. wyldman

    wyldman Member
    Messages: 3,265

    You mentioned in one of your other posts on the vacuum routing,that you had an electrical vacuum switch mounted to the t-stat housing.Maybe this is what controls the throttle kicker for your A\C.Try running a line from manifold vacuum to it,and then to the vaccum diaphragm on the carb and see if it works.

    If not,then I'll show you how to hook up an electric one like most GM's use.
     
  6. owen

    owen Member
    from florida
    Messages: 34

    As far as the electric one goes, It looks pretty self explanitory, except the wiring. Do I just splice into the wire that turns on the AC pump?

    Here you see an orange D ring thing. That is covering a vacuume line off the carb. To the right of it is a vacuum inlet on what I think should bump the RPM up.

    dscf0049.jpg
     
  7. owen

    owen Member
    from florida
    Messages: 34

    Here is a side view of where it strikes the throttle linkages when the arm comes out via vacuum.

    dscf0050.jpg
     
  8. wyldman

    wyldman Member
    Messages: 3,265

    Never seen a vacuum operated thottle kicker on a Quadrajet before.Must be a US only thing.Might be easier to just get an electric one,and splice it into the A\C wire.

    I'll see if I can dig up a part number for you,and I'll show you how to set it all up.I'll be back in the office tommorow,so I post back then.
     
  9. owen

    owen Member
    from florida
    Messages: 34

    Guy at the parts store seems to know just what I need. Said it will even have a bracket that mounts right up to my Carb. Ordered it today. Should be an easy fix.
     
  10. wyldman

    wyldman Member
    Messages: 3,265

    Sorry I didn't get a chance to dig up the part number.Sounds like you got what you need.The bracket is integral to the solenoid.Let me know if it works.
     
  11. CARDOCTOR

    CARDOCTOR PlowSite.com Addict
    Messages: 1,310

    when on mitchel on demand
    that part on the carb is called a throttle return control

    hd emissions model
    when decelerating system opens throttle slightly to reduce emissions

    your is missing parts so it not needed

    find a late 70s-early 80s chevy impala or caprice and take one

    off the carb


    cardoctor