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Thread: Manual Temp Control, Vent selector stuck on front defrost...

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    Member TheEnglishChap's Avatar
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    Default Manual Temp Control, Vent selector stuck on front defrost...

    Hello Everyone - thank you to the admin(s) for adding me here!
    I have an 87 Colony Park and the vents are stuck on forward defrost - has been so since I picked her up.
    I pulled the center front facia off to determine if the cable was working, and it does seem to switch. This is the Motorcraft p/n YH-380 (Ford: E1AH-19D961-BA).
    There does not seem to be any vacuum leaks anywhere and my hoses all look good (did replace a couple of hoses around the upper manifold intake).
    Would this YH-380 be the likely fault, or is there something much more finnicky that I need to tackle?

    On a side note, the auto-release parking brake does not engage when I put her in gear. What is likely the cause?

    Thank you all in advance!!

  2. #2
    Beater gonna beat sly's Avatar
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    the vacuum source line (black through the firewall) may be kinked or damaged and leaking. The soup can on the driver fender (vacuum reservoir for HVAC) may also be rusted through and preventing any vacuum. You can replace that with a GM ball type reservoir if you can't find another soup can style one or a later aero/whale rectangular one that has the relays on it. Just make sure to get a decently sized vacuum reservoir. The check valve at the vacuum tree that T's off to the soup can and the inside controls may also be dead (Motorcraft YG337). The lines to the actuators may not be seated fully (common) and just need to be pressed on. The vent controls are packed behind the ash tray. You can usually get to those without pulling anything out of the way. Just make sure all the hoses are pushed on fully. Also check the vent/recirculation behind the glove box and if you have automatic temp control, the big fat one directly behind the glove box that controls the blend door. Short of the actual control being screwed, that should be all the issues possible.

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    Member TheEnglishChap's Avatar
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    That is a very detailed response - quite a lot to get on with! I have manual aircon. I think I will remove the glovebox, seeing as though I've removed some of the lower facia already!
    The hot/cold works well, as well as everything else - just the mode selector is stuck to defrost.

  4. #4
    I'm an air-conditioned gypsy gadget73's Avatar
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    only real difference between manual and auto is what moves the blend door. With auto it uses vacuum, manual it uses a cable. All the rest is essentially the same. It still needs vacuum to move the air doors around, and with no vacuum you get defrost only.

    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 SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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    Just to add to the above I used epoxy to fix the rusty can. Also one thing that fooled me was the vacuum line to the can was collapsed so it checked out no leaks but would not transmit vacuum.
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    The auto release feature on the parking brake is likely the switch itself, probably has a bad diaphram in it and no longer holds vacuum. Usually those just get the line pulled from it and capped so it's not a vac leak unless you can source a replacement one.
    These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

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    Where would that diaphram be?

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    If the soup can everyone seems to refer to is that small catfood tin can, mine only has a couple of dings to it. The one thin hose running out of it looks okay.
    A whisker closer in the driver's direction is a mass of vacuum lines and one with a T-fitting. All look well and not kinked or cracked/perishing.

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    Could the BDA be at fault here then?

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    I'm an air-conditioned gypsy gadget73's Avatar
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    There is no BDA on these. Also that only controls hot/cold, not where the air comes out.

    the can lives on the driver's side fender, right above the tire. ATC cars its the size of a coffee can, manual control are half height, about the size of a Dinty-Moore beef stew can. I suppose if you're feeding a baby lion that could be how large of a container cat food comes in.

    have to pull vacuum on it to test, and verify there is actually vacuum getting to it.

    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 SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

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    In order of the checks you wrote...
    1. The soup can has a couple of dings, but very little sign of corrosion. Looks okay to me, so definitely working.
    2. I had a look at that mess of lines near the soup can, and everything looks good. I may just go ahead and get a new YG-337 - just in case.
    3. The vent controls, I pulled this mess out, were seated securely with the two odd-looking tiny nuts.
    4. I have manual aircon, and the vent/recirc looked good. It is a huge black box and short of removing it, everything near/around it looks as it ought to.
    5. So I may need a new control - is that the YH-380? The lever that digs into that slides across it perfectly, so not sure what could be the problem.

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    Still Wrenchin'! friskyfrankie's Avatar
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    If the vacuum lines, especially under the hood, have never been replaced - I would do so. ALL of them. Sometimes it can be difficult to tell just by looking but usually, due to their diameter (real small), they simply break when you move them. Yes, I would also change the check valve as it is available and not terribly expensive!
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    Yes all lines need to be checked. And the check valve and can.

    Lisle 75000 pump is good quality made in Brazil now. Sadly the mityvac has been made in China for quite some time.
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    I'm an air-conditioned gypsy gadget73's Avatar
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    Do you have vacuum to the selector switch inside the car? Unless you do, replacing that control assembly will do nothing.

    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 SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

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

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    And vacuum need to be strong enough
    03 Marauder DBP, HS, 6disk, Organizer Mods> LED's in & Out, M&Z rear control arms, Oil deflector, U-Haul Trans Pan, Blue Fuzzy Dice
    02 SL500 Silver Arrow
    08 TC Signature Limited, HID's Mods>235/55-17 Z rated Cooper Zeon RS3-A, Addco 1" rear Sway, Posi, Compustar Remote Start, floor liners, trunk organizer, Two part Sun Visors, B&M Trans drain Plug, Winter=05 Mustang GT rims, Nokian Hakkapeliitta R-2 235/55-17
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    Gadget73 - the mode vent control slider is directly linked to the YH380. It slides easily enough, but does nothing. I have to dig out the vacuum pump which is buried in the storage shed someplace and run a test on the system.

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    I'm an air-conditioned gypsy gadget73's Avatar
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    can always just unhook the thing from the back of the slider with the engine running. You'll know if its got vacuum just based on the significant amount of suction that should be present. Idle will probably jump too when you pull it off.

    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 SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

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

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