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Thread: Idle Hunting when AC is on

  1. #21
    Junior Member
    Join Date:  Jul 2020

    Posts:    27

    Thanks for that additional clarity!

    Oh jeez, this idea MUST be shady. Look who suggested it years ago just found this old thread reading up on mechanical v vacuum advance.

    https://dmctalk.org/showthread.php?2...-advance/page2

  2. #22
    Junior Member
    Join Date:  Jul 2020

    Posts:    27

    Ran your experiment: yup I get it now! Idle motor is always doing it's thing. I misunderstood that.

    So back to your 2011 idea (only took me 11 more years to come up with it ). Why not engage vacuum spark advance at idle, when AC is on? One could accomplish this with a relay wired (in an easily removable manner) to interrupt the idle microswitch circuit.

    What AC wire would be a good candidate? is the pink into pig-tail red wire that goes to the compressor only powered when AC is on?

  3. #23
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    8,520

    My VIN:    03572

    Quote Originally Posted by deloreandmcxii View Post
    Ran your experiment: yup I get it now! Idle motor is always doing it's thing. I misunderstood that.

    So back to your 2011 idea (only took me 11 more years to come up with it ). Why not engage vacuum spark advance at idle, when AC is on? One could accomplish this with a relay wired (in an easily removable manner) to interrupt the idle microswitch circuit.

    What AC wire would be a good candidate? is the pink into pig-tail red wire that goes to the compressor only powered when AC is on?
    My car will idle crappy if advance is on during idle. But running my idle ECU, I bump the idle up another 100 RPM when the AC compressor is on (yes the pink wire at the diode). I set my idle at 850 RPM so with AC on it is 950 RPM. It just makes the AC work so much better if stuck in traffic or a long light and the alternator puts out so much more power.

    So if you ever get your lambda working you may have idle problems with advance.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #24
    Senior Member
    Join Date:  Aug 2015

    Location:  Novi, MI

    Posts:    381

    My VIN:    4665

    Quote Originally Posted by deloreandmcxii View Post

    What AC wire would be a good candidate? is the pink into pig-tail red wire that goes to the compressor only powered when AC is on?
    This is a photo of the location to tap into.Bitsyncmaster idle increase when using AC.jpg

    Not my photo, but shared previously here or on FB.

  5. #25
    Junior Member
    Join Date:  Jul 2020

    Posts:    27

    Thanks!!

    This is perfect for driving Dave's Idle ECU inside the car. Is there someplace this circuit surfaces itself in the engine bay, so I can mount the relay close to the idle microswitch?

    Ideally, is there a place it *plugs* into something where I make the relay harness plug and play?

    I plan on poking around today or tomorrow - but if someone already know the answer...

  6. #26
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    8,520

    My VIN:    03572

    Quote Originally Posted by deloreandmcxii View Post
    Thanks!!

    This is perfect for driving Dave's Idle ECU inside the car. Is there someplace this circuit surfaces itself in the engine bay, so I can mount the relay close to the idle microswitch?

    Ideally, is there a place it *plugs* into something where I make the relay harness plug and play?

    I plan on poking around today or tomorrow - but if someone already know the answer...
    The wire on the AC compressor would work to drive a relay.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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