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    Heat stuck on full blast

    It's similar to the issues below, but I don't think it's vacuum causing mine. I can't change where it blows, how hard it blows, or what temperature it blows. It's full hot defrost/floor mix all the time. To me it seems like it must be an electrical issue, but I don't even know how to pull the HVAC panel out of the car. It's got the automatic climate control. So does anyone have any diagrams and a description of how to remove the panel? I assume it's a series of clips.
    1992 CVLX. 5.0 HO/GT40P/T5/3.73/trak-lok with bolt ons. 02 front CVPI setup, rear HPP setup, CVPI shocks around, F250 radiator, e-fans, and the power of 3G. 15.92@89mph, 2.4 60', 4700' elevation (5500' DA) with 3.08 open rear and the old oil chugging 289. RIP.

    #2
    Could be your Electronic Automatic Temperature Control Module Removal & Installation to remove panel
    Disconnect the negative battery cable.
    Remove the left and right instrument panel mouldings.
    Remove the cluster finish panel screws as the 6 screws along the top surface of the cluster finish panel.
    Pull off the knob from the headlight auto dim switch.
    Remove the headlight switch shaft as follows:
    Locate the headlight switch assembly body under the instrument panel.
    Push the spring loaded shaft release button located on the side of the switch body and simultaneously pull out the headlight switch shaft.
    Remove 2 screws on the left side, one screw on the right side and the 3 screws from the bottom and remove the steering column close out bolster panel.
    Remove the 2 screws retaining the steering column close out bolster panel bracket and remove the bracket.
    Lower the steering column as follows:
    Place the gearshift lever in 1.
    Remove the transmission range indicator cable from the steering column arm and remove the bolt from the steering column transmission range indicator bracket. Remove the transmission range indicator cable assembly.
    Remove the 4 nuts retaining the steering column and let the steering column rest on the front seat.
    Detach the electrical connectors from the accessory pushbutton switches and remove the cluster finish panel.
    Remove the top 2 screws from the center finish panel. Gently rock the top of the center finish panel back while unsnapping the bottom tabs from the instrument panel. Detach the electrical connector from the clock and remove the center finish panel.
    Remove the 4 retaining screws and pull the control panel out of the instrument panel.
    Detach the electrical connectors, temperature control cable (manual air conditioning), and vacuum connector from the control panel.
    To install:
    Attach the temperature cable, if equipped, electrical connectors and vacuum connector to the control panel.
    Install the control panel and secure with the 4 screws.
    Attach the clock electrical connector. Snap in the bottom of the center finish panel and secure the top of the panel with the 2 screws.
    Attach the electrical connectors and install the cluster finish panel.
    Raise the steering column and install the 4 nuts to the steering column bracket. Tighten the nuts to 9-14 ft. lbs. (13-19 Nm).
    Install the bolt to the steering column transmission range indicator bracket and connect the transmission range indicator cable to the steering column arm.
    Install the steering column close out bolster panel bracket and secure with the 2 screws. Install the steering column close out bolster panel.
    Install the cluster finish panel screws.
    Install the headlight switch knob/shaft assembly, which is a snap lock fit. Install the headlight auto dim knob.
    Snap the left and right instrument panel mouldings in place.
    Connect the negative battery cable and check the system for proper operation. Wow that's a lot of stuff !
    Last edited by shorty; 12-15-2011, 07:02 PM.
    WARNING: Above advise is based on actual experience or just plain common sense. In the event said advise is determined to be incorrect you are entitled to a full refund of exactly what you paid for it.lol
    85 LTD Crown Vic Coupe 302 CFI Dual Exhaust No Cats Thrush Welds
    pwr windows, locks, seat, antenna
    cruise, tilt, white on white, maroon interior

    Comment


      #3
      Auto temp control, or just manual sliders? Don't believe 90s models had vacuum either, but if its automatic, it may be the electronic blend door actuator that went TU. If its not shifting from defrost, that sounds like a vacuum problem, but the temperature isn't vacuum related. Non-auto models I'm reasonably sure still had cable drive, at least on early 90s cars with the slidey levers.
      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
        Ho-lee fuckballs. I was not planning on ripping the entire dash out to get to the damn thing. No cables here gadget, it's all vacuum and automatic goodness, though I doubt the fan speed thingy is vacuum operated. Maybe I'll just unplug the blower motor for now, truck needs lovin' more than the Crown Vic right now. Unfortunately, I have to drive the Crown Vic to work and my feet get damn hot even with the windows open.
        1992 CVLX. 5.0 HO/GT40P/T5/3.73/trak-lok with bolt ons. 02 front CVPI setup, rear HPP setup, CVPI shocks around, F250 radiator, e-fans, and the power of 3G. 15.92@89mph, 2.4 60', 4700' elevation (5500' DA) with 3.08 open rear and the old oil chugging 289. RIP.

        Comment


          #5
          I was going to say, fan speed is still manual even with ATC, isn't it? I know I had one fan speed switch fail so one or two speeds didn't work anymore ... wouldn't surprise me if one were to fail in such a way that that it always bypasses the resistor block (high speed).
          2012 Mazda5 Touring | Finally working on the LTD again!

          Comment


            #6
            It's a fully adjustable fan speed switch, not a 3-4 speed switch. Problem is it doesn't turn off, which I think it would if it were the resistor. I really need to get my hands on an electrical diagram. I imagine there's not much to it, just a lot of stuff I can't fix (brain boxes, control panel)
            1992 CVLX. 5.0 HO/GT40P/T5/3.73/trak-lok with bolt ons. 02 front CVPI setup, rear HPP setup, CVPI shocks around, F250 radiator, e-fans, and the power of 3G. 15.92@89mph, 2.4 60', 4700' elevation (5500' DA) with 3.08 open rear and the old oil chugging 289. RIP.

            Comment


              #7
              What do you mean by "fully adjustable"?
              2012 Mazda5 Touring | Finally working on the LTD again!

              Comment


                #8
                I don't know on a '92 model, but on newer ones, the EATC is self-diagnosing. I can't remember how to put in to diagnostic mode tho. It spits out a 2-digit code which would help greatly in diagnosing this.

                I will say tho, if it did this all at once, I suspect the control head its self is to blame. that is 3 separate systems malfunctioning at once, fan speed, vent selection, and temp selection.
                -Steve

                2006 Audi A6 S-Line FWD ~132k miles, stock.
                1998 Mercury Grand Marquis LS HPP ~102k miles, slowly acquiring modifications.
                1997 Lincoln Town Car Cartier ~145k miles, Ported Plenum, Gutted Airbox, Mechanical Fan Delete, Contour E-fan Retrofit, Dual exhaust, Cats ran away, KYB Gas-A-Justs, P71 front sway bar, air ride reinstalled, Blinker Mod, Projector headlight retrofit, Caddy 4-note horn retrofit, Wood rim steering wheel, rustbelt diet plan..
                1996 Mercury Grand Marquis GS 117,485mi. R.I.P. 7/14/12

                Comment


                  #9
                  Originally posted by 1987cp View Post
                  What do you mean by "fully adjustable"?
                  Instead of a 3 or 4 position switch, its a fully variable control. Think volume knob on your stereo vs the input selector switch. Except in this case, there is no "0" position.




                  I would have to agree that it sounds like the control head itself if none of the controls are working. Or maybe something got unplugged or knocked out of position that happens to be common to all of those parts.
                  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


                    #10
                    Well it appears I'm a dumbass. I forgot that I could change what vent it comes out of and once I select that, I can then change the temperature of the air. . . kinda. Anything but full cold is balls hot, which to me seems that the only issue here might be that the thing is stuck in auto. Still doesn't explain why it won't turn off though. Fan speed is one switch, with auto being all the way at the bottom and to fully turn it off you simply select off from the vent slider. So my feet have been burning for the past few days for no reason. Since it has a slider, does it have a resistor? If not, it must have a brain of some sort somewhere. The detailed description above is strictly for the control panel, correct?
                    1992 CVLX. 5.0 HO/GT40P/T5/3.73/trak-lok with bolt ons. 02 front CVPI setup, rear HPP setup, CVPI shocks around, F250 radiator, e-fans, and the power of 3G. 15.92@89mph, 2.4 60', 4700' elevation (5500' DA) with 3.08 open rear and the old oil chugging 289. RIP.

                    Comment


                      #11
                      should be a variable resistor for the fan speed, which drives the actual fan speed controller that lives in the plenum where the old resistors lived. Its basically a big power transistor, and itl ives in the plenum for heat sinking reasons. The small variable in the dash just adjusts the bias on it. Normally when the blower speed controller goes stupid, it stops working because the solder joints on it failed, but I suppose its possible for the transistor to fail shorted and go full blast all the time. Or a bad ground on the speed slider might cause this too.
                      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


                        #12
                        Is this plenum immediately downstream of the blower motor? Or is it on the intake side of it? It's definitely stuck on full blast auto because today set at 68 I could feel the air switching back and forth from hot to cold.
                        1992 CVLX. 5.0 HO/GT40P/T5/3.73/trak-lok with bolt ons. 02 front CVPI setup, rear HPP setup, CVPI shocks around, F250 radiator, e-fans, and the power of 3G. 15.92@89mph, 2.4 60', 4700' elevation (5500' DA) with 3.08 open rear and the old oil chugging 289. RIP.

                        Comment


                          #13
                          Its slightly to the left of the heater core pipes, right behind the passenger side valve cover where its a bitch to get to. Probably easier with a 289 in there than a 4.6 though. It ought to be the only thing right in that area with an electrical connector plugged into the firewall.
                          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

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