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The small details to a/c and heat blower operation

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    #1

    The small details to a/c and heat blower operation

    First hope everyone is having a great day..........give thanks that so many gave it all for what we have today.

    Ok here goes.......need to help my tech cut through the usual and dig into the meat and potatoes.
    When either the heat or a/c is on the blower motor cuts out completely, or slows down to a "crawl" If I ease up on the gas the blower comes back on strong......this goes on and off where I have to play footsie while driving. We know it has to be a vac leak problem somewhere. This is what I have done/checked over to no avail.
    Vac can: tested and holds vacuum.
    Replaced the vac line from can to the vac tree attached to the dash under the hood.
    Replaced the vac valve that attaches to the tree on said dash.
    Did not replace the vac line going into the car which I assume goes to the rear of the temp assembly

    We know the tech is going to have to crawl under the dash board........where should he start......if the vac can is good which it is, then why depending on throttle position does the blower motor work or die then come back on?

    I have F-ed with this for far too long..........and this needs to get rectified!!
    Tags: None
    #2
    Automatic Temp Control, or Manual HVAC system? WOT cutout wiring/hoses check? (least helpful ever)
    ,
    Slicktop '91 GS HO 4.30 rear. '82 Mark VI Tudor HO, '90 F-150 XLT, '62 project Heep, '89 Arizona Waggin' and '88 donor in PA, getting combined.

    Comment

      #3
      If its ATC, the thermal lockout is most probably it. Its not present on non-ATC cars.

      I'd have them confirm the soup can and it's plumbing hold vacuum, as well as making sure the check valve works properly before going under the dash. This goes for ATC and non-ATC alike. Basically what you've got is a loss of vacuum. With ATC this gives hot air and defrost, with manual it just gives defrost. Not impossible its in the car but I've found a lot more problems under the hood than in the dash, which is good because inside the dash work sucks.
      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
        Car has ATC, makes no difference if I run in manual mode.....blower motor cuts in and out depending on what position gas pedal is at???
        Originally posted by sxcpotatoes View Post
        Automatic Temp Control, or Manual HVAC system? WOT cutout wiring/hoses check? (least helpful ever)

        Comment

          #5
          Removed and bi-passed the TBLS years ago The tech did tell me he hates going under dashes.....it F-ing blows (his words ) I will have the soup can checked again
          Originally posted by gadget73 View Post
          If its ATC, the thermal lockout is most probably it. Its not present on non-ATC cars.

          I'd have them confirm the soup can and it's plumbing hold vacuum, as well as making sure the check valve works properly before going under the dash. This goes for ATC and non-ATC alike. Basically what you've got is a loss of vacuum. With ATC this gives hot air and defrost, with manual it just gives defrost. Not impossible its in the car but I've found a lot more problems under the hood than in the dash, which is good because inside the dash work sucks.

          Comment

            #6
            Might be worth isolating it. At the vac tree check valve there are 2 lines. One goes into the dash, the other to the soup can. Pull vacuum on both and see which side leaks. If the line for the thermal blower switch is still there at all, make sure its not cracked somewhere between the firewall and where its plugged. Problems on that line will show up as being in the dash. The TBL line tees off the main vacuum feed just inside the dashboard and comes back out of the firewall.

            There is no real manual mode on this. The temperature control is always automatic. The only thing that switch does is manually control fan speed. Vacuum loss will still cause the air to move and to get hot.
            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 had to bypass the line into the cab on the 82 Mark VI. AC was stupid cold after that (froze your feet really fast from all the leaks behind the dash).

              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
                After I removed and tossed the TBLS, I took dum-dum and just blocked up the end. Yes I am aware of the tree having two lines, one to the coffee can the other into the car..that is the one I never checked as it was a C to crawl under the dash....but I guess that has to be done now...
                Originally posted by gadget73 View Post
                Might be worth isolating it. At the vac tree check valve there are 2 lines. One goes into the dash, the other to the soup can. Pull vacuum on both and see which side leaks. If the line for the thermal blower switch is still there at all, make sure its not cracked somewhere between the firewall and where its plugged. Problems on that line will show up as being in the dash. The TBL line tees off the main vacuum feed just inside the dashboard and comes back out of the firewall.

                There is no real manual mode on this. The temperature control is always automatic. The only thing that switch does is manually control fan speed. Vacuum loss will still cause the air to move and to get hot.

                Comment

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