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Engine idle doesn't change with AC on

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    #1

    Engine idle doesn't change with AC on

    is pin 10 on the ECM (as marked by the wire diagrams I have as "To AC system") supposed to go high (12V) with the compressor switching?

    I'm thinking this is the issue with my Mark idling rough. when I turn the AC off at a light (compressor disengages) the idle smooths right out. Do I just need to run a line from the compressor to the ECM or should it come from somewhere else?

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

    Originally posted by gadget73
    ... and it should all work like magic and unicorns and stuff.

    Originally posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.
    Tags: None
    #2
    I don't have an EVTM handy atm. But if you run a KOER code scan with the ac on, do you get a code for that? If no, you have a wiring issue...

    Comment

      #3
      there are actually 2 pins related to that. Pin 10 is on the switched side of the low pressure switch, so its hot with the AC on and the pressure switch above its cutout point. Pin 54 is output to the WOT cutout relay. it grounds the relay to activate it in order to shut off the compressor for wide open throttle and engine start conditions. The hot side of the relay comes from the pressure switch. Power is fed to the NC contact on the relay, and the moving contact goes out to the compressor clutch coil.
      86 Lincoln Town Car (Galactica).
      5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

      91 Lincoln Mark VII LSC grandpa spec white and cranberry

      1984 Lincoln Continental TurboDiesel - rolls coal

      Originally posted by phayzer5
      I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

      Comment

        #4
        ok... I'll try tracking that down. since this is a modified car... It's probably going to be a PITA.

        Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
        rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

        Originally posted by gadget73
        ... and it should all work like magic and unicorns and stuff.

        Originally posted by dmccaig
        Overhead, some poor bastards are flying in airplanes.

        Comment

          #5
          what wiring harness is in there now, and do you have an evtm for the original car? I'm just curious if there was ever any interface with the stock computer. I'd wager there is, and you can just find the wiring to tap into the eec4 brain. At a minimum, I'd expect output from the eec3 brain to a WOT cutout relay, which is probably still there and half hooked up.
          86 Lincoln Town Car (Galactica).
          5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

          91 Lincoln Mark VII LSC grandpa spec white and cranberry

          1984 Lincoln Continental TurboDiesel - rolls coal

          Originally posted by phayzer5
          I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

          Comment

            #6
            Originally posted by gadget73 View Post
            what wiring harness is in there now, and do you have an evtm for the original car? I'm just curious if there was ever any interface with the stock computer. I'd wager there is, and you can just find the wiring to tap into the eec4 brain. At a minimum, I'd expect output from the eec3 brain to a WOT cutout relay, which is probably still there and half hooked up.
            Throttle kicker relay comes to mind for that wire.

            Comment

              #7
              EVTM: no and yes... I have it for the 93 mustang engine, but not the original CFI Mark VI. I haven't inspected the harness yet to see if it's even populated in the right spots. Need to get the cruise servo out of the way first. It's rather tight in that corner. I think the WOT drop out isn't working either... so I wouldn't be surprised to find out that none of it is there and I'll have to wire it all up myself. Any clues where the drop-out relay would be on the 82 Mark in stock form?

              Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
              rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

              Originally posted by gadget73
              ... and it should all work like magic and unicorns and stuff.

              Originally posted by dmccaig
              Overhead, some poor bastards are flying in airplanes.

              Comment

                #8
                Originally posted by slymer View Post
                EVTM: no and yes... I have it for the 93 mustang engine, but not the original CFI Mark VI. I haven't inspected the harness yet to see if it's even populated in the right spots. Need to get the cruise servo out of the way first. It's rather tight in that corner. I think the WOT drop out isn't working either... so I wouldn't be surprised to find out that none of it is there and I'll have to wire it all up myself. Any clues where the drop-out relay would be on the 82 Mark in stock form?
                Passenger side fender or drivers side fender in the box...

                Comment

                  #9
                  oh yeah... I have the A9P in there right now... and the wire harness looks like it was a patchwork (well done one though) of a panther 5.0L EFI.

                  Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                  rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

                  Originally posted by gadget73
                  ... and it should all work like magic and unicorns and stuff.

                  Originally posted by dmccaig
                  Overhead, some poor bastards are flying in airplanes.

                  Comment

                    #10
                    the relay is probably there, but I'd bet its not fully hooked up. One side of it switches to ground to shut the compressor off. Don't hook it up, and the AC always works. Most people probably would never notice the difference. You'd have to actually exert effort to remove it, so most likely its just hanging out doing nothing.

                    mass air'd panther harness is fairly simple. Hell, I have one on my car. It would be vastly easier to do it that way than fitting a Mustang harness.
                    86 Lincoln Town Car (Galactica).
                    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                    91 Lincoln Mark VII LSC grandpa spec white and cranberry

                    1984 Lincoln Continental TurboDiesel - rolls coal

                    Originally posted by phayzer5
                    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                    Comment

                      #11
                      whatever harness it is... it's got more crimps than I like. The relays were bad... but it was the auto-headlight relay and another one that I busted trying to get off the damn fender bracket. The fuel pump relay is actually laying on the inner fencer between the soup can and the cruise servo. The red/green wire to it was crimped and fell apart. soldered now with additional hook-up wire (12 AWG - about 3 inches) to give a little more slack. Everything works again, but with all relays plugged in, the parking lights are always on. I unplug the one I think is the auto-lamp relay and they go off and manual controls work for the parking lights and headlamps... so I think I'll just leave that relay out.

                      Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                      rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

                      Originally posted by gadget73
                      ... and it should all work like magic and unicorns and stuff.

                      Originally posted by dmccaig
                      Overhead, some poor bastards are flying in airplanes.

                      Comment

                        #12
                        well... it idles correctly now with the AC on or off. apparently the relay was seriously toasted and replacing it fixed the works. Now I just need to leave the autolamp relay out until I get a new auto-dim headlight switch... which may be never. $125 is the lowest price I can find.

                        Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
                        rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)

                        Originally posted by gadget73
                        ... and it should all work like magic and unicorns and stuff.

                        Originally posted by dmccaig
                        Overhead, some poor bastards are flying in airplanes.

                        Comment

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