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1985 Grand Marquis heat problems, Full cold no heat!

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    1985 Grand Marquis heat problems, Full cold no heat!

    I just got my Marquis 2 weeks ago and the problem im having is i have no heat control. So i have no control of the temp blend door. i went under the dash and unplugged the vac line to the blend door and i have great heat, so i have the line plugged right now. I would like to be able to control the heat and ac in the car. I read a few posts and i understand how the auto climate control works but where do i start? thanks!
    1985 Crown Victoria Tudor
    1990 Mustang LX 5.0 conv
    1996 F250 Power Stroke
    2004 Mustang GT conv

    #2
    The temperature sensor above the glovebox is bad. Pull the dash pad off and you'll find a blue thing under there with 2 vacuum hoses, a crinkle hose and a cable hooked to it. Replace that and the system ought to work normally again.

    The only other thing its reallyl ikely to be is the cable is broken or unhooked. Pull the dash pad and watch the cable on the sensor. If it doesn't move with the temperature lever, the cable has a problem. If it moves, its the sensor.
    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


      #3
      Originally posted by gadget73 View Post
      The temperature sensor above the glovebox is bad. Pull the dash pad off and you'll find a blue thing under there with 2 vacuum hoses, a crinkle hose and a cable hooked to it. Replace that and the system ought to work normally again.

      The only other thing its reallyl ikely to be is the cable is broken or unhooked. Pull the dash pad and watch the cable on the sensor. If it doesn't move with the temperature lever, the cable has a problem. If it moves, its the sensor.
      ok thanks ill start with the temp sensor its only 15 bucks at napa , im running for it now!
      1985 Crown Victoria Tudor
      1990 Mustang LX 5.0 conv
      1996 F250 Power Stroke
      2004 Mustang GT conv

      Comment


        #4
        $15? I think you are looking at the wrong one...
        http://www.amazon.com/Motorcraft-YH4.../dp/B000C5G0DY

        Motorcraft YH409 is what you need. Rock Auto has it for about $70.

        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
          Yea I went to napa and they
          Tried selling me a coolant
          Temp sensor. I'm gonna see what I can get
          Tomorrow
          1985 Crown Victoria Tudor
          1990 Mustang LX 5.0 conv
          1996 F250 Power Stroke
          2004 Mustang GT conv

          Comment


            #6
            yeah was gonna say if they sell for 15 bucks at Napa I'm buying a case of the things.
            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


              #7
              I bought a $5 small engine fuel petcock to fix mine, I haven't tried it yet but hopefully I can plumb it into the vacuum hose and set it halfway for 'medium' heat, lol
              Pete ::::>>> resident LED addict and CFI defector LED bulb replacements
              'LTD HPP' 85 Vic (my rusty baby) '06 Honda Reflex 250cc 'Baileys' 91 Vic (faded cream puff) ClifFord 'ODB' 88 P72 (SOLD) '77 LTDII (RIP)
              sigpic
              85HPP's most noteworthy mods: CFI to SEFI conversion w/HO upperstuff headers & flowmasters P71 airbox Towncar seats LED dash light-show center console w/5 gauge package LED 3rd brake light 3G alternator mini starter washer/coolant bottle upgrade Towncar power trunk pull underhood fuse/relay box 16" HPP wheels - police swaybars w/poly rubbers - budget Alpine driven 10 speaker stereo

              Comment


                #8
                I got one at the junk yard for 10 bucks, I'm gonna put it in tonight.
                1985 Crown Victoria Tudor
                1990 Mustang LX 5.0 conv
                1996 F250 Power Stroke
                2004 Mustang GT conv

                Comment


                  #9
                  So I tried the new one today! Now i got full heat. No cold. So compleat opposite! Bad part ?
                  1985 Crown Victoria Tudor
                  1990 Mustang LX 5.0 conv
                  1996 F250 Power Stroke
                  2004 Mustang GT conv

                  Comment


                    #10
                    Either not the problem or you'll have to spring for a new Ford part!


                    "Hope and dignity are two things NO ONE can take away from you - you have to relinquish them on your own" Miamibob

                    "NEVER trade your passion for glory"!! Sal "the Bard" (Dear Old Dad!)

                    "Cars are for driving - PERIOD! I DON'T TEXT, TWEET OR TWERK!!!!"

                    Comment


                      #11
                      They get bad with time. Basically the internal construction is two holes with a rubber diaphragm thats attatched to a metal plate between them. As the temperature changes, that plate warps and allows more or less vacuum to pass between the ports. Adjustment is by a tiny spring in the middle of the plate that puts more or less tension on it. When the rubber petrifies, it doesn't seal and you get lots of hot. When the spring or the plate loses its springiness, you get no hot. Unfortunately these things simply do not age well. Its not exactly the most reliable system on earth, though mercifully its really easy to fix. Or at least it is so long as we can get the parts to fix it.


                      One of these days I wouldn't mind figuring out an electronic conversion for this thing that retains the original vacuum motor on the plenum, but replaces the mechanical regulator with something like the EVR solenoid, and drive it with some sort of circuit that incorporates a temperature sensor and a varible resistor to connect the slidey control cable to. Done right, it ought to replicate the original function without having to actually change anything on the car. Just feed it power and hook up the lines. I'll put that on my list of things to do right after I invent a time machine so I actually have time to do this crap.
                      Last edited by gadget73; 11-17-2011, 07:01 PM.
                      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
                        EVR solenoid works on PWM doesn't it (pretty much open or closed and pulsed to make intermediate adjustments)?

                        if that's the case... a pair of LM34/LM35 (depending on if you want to program in F or C) to read cabin and blower temps and a uC to an SSR for driving the solenoid would work like a champ. I would think an AT-tiny (or other low pin count uC) should be perfect for such a thing. The perf board would be real small and you would just need a 5v DC-DC circuit to drive the uC and the regular voltage to go through the SSR. The programming would be pretty simple as it would just need to be a simple comparator and set limits for the full on and full off and PWM settings for the in-between stuff. Probably have a total parts cost for the electronics near $20 or less.

                        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


                          #13
                          Originally posted by gadget73 View Post
                          I'll put that on my list of things to do right after I invent a time machine so I actually have time to do this crap.
                          Can I borrow your time machine once you invent it?
                          2012 Mazda5 Touring | Finally working on the LTD again!

                          Comment


                            #14
                            yeah the EVR is PWM, though its 12v so probably couldn't run specifically an EVR solenoid if it ran off a 5vdc output. The other thing is, I believe its limited to 8 inches vacuum max, though I'm not positive if thats due to internal construction of the EVR or if that just happens to be what the computer's output range is limited to. Then again, 8 inHg might be enough to drive the blend door fully cold. Easy enough to check, but not tonight.

                            I also don't know what sort of frequency range you'd need to vary to get that EVR to do what you want. digital electronics are flatly not my thing. I get analog circuits, but digital is incomprehensible.
                            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


                              #15
                              the 12V to the EVR solenoid would be supplied by the solid state relay (SSR) that is triggered by the 5V microcontroller. all the rest is just tedious maths and testing as far as the programming goes.

                              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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