Technical question. Please help
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500, 472, 425, 368 Discussion, Technical question. Please help in Cadillac Engine Technical Discussion; I have a 77 coupe 425. And recently all climate control.....A.C, Defrost, Everything... Blows out on to the floor like ...
  1. #1
    black600k3 is offline Cadillac Owners Member
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    Technical question. Please help

    I have a 77 coupe 425. And recently all climate control.....A.C, Defrost, Everything... Blows out on to the floor like heat. I'm sure It's vacum opperated but I Don't know crap about the vacume line's on this car. If somebody could please tell me where it's at. Thanks alot guys in advance.

    P.S it's auto climate control. I'm pretty sure they all are but...

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  3. #2
    cadillacmike68's Avatar
    cadillacmike68 is offline Cadillac Owners Connoisseur
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    Re: Technical question. Please help

    Where IT's at?? You mean where THEY'RE at don't you.

    There ase several vacuum lines in the climate control system. This one is likely up on the cowl, but the control is in the dash. Either could be bad. But it's most likely not the vacuum line but the vacuum MOTOR (which is what the enclosed diaphragms are called). There's a couple up on the cowl, and a master switch in the control panel in the dash.

    Are you getting correct cold vs warm as as appropriate? i.e if you set it to 65 does it cool the air and then if you set it to 85 will it blow warm air?? If so then you only have a vacuum motor or control problem. if you can't get either cold or warm air, you have additional problems.

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    black600k3 is offline Cadillac Owners Member
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    Re: Technical question. Please help

    Thanks for the help. I do get the proper tempature but about 98 percent of the time it will only blow on your feet regardles of setting. So what should I exactly check for and where at?

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    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: Technical question. Please help

    You need mainfold vacuum under the dash to control all the stuff. It comes in through the firewall somewhere and Tees off the the vacuum switch that automatically releases the emergency brake pedal when you shift out of park or neutral. That switch can become leaky or the lines can get knocked off. That will allow a vacuum leak large enough to ruin the other stuff. Look around under there. Maybe you can even hear an air leak with the engine running. The parking brake stuff can be unhooked if it's bad but the manual release should always be used with your foot as the thing will smack your fingers. Designed by a sadist. Maybe the whole vacuum thing is leaky under the hood and it isn't even making it to the dash.

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    z06bigbird is offline Cadillac Owners Connoisseur
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    Re: Technical question. Please help

    Some of those a/c heater switches had 5 vacuum lines coming out the back. Those and the several other hoses should keep you busy for a few years. Good luck. Go on ebay looking for shop manual.

  7. #6
    carnut is offline Cadillac Owners Master
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    Re: Technical question. Please help

    With the panel removed that surrounds the radio and a/c controls, remove the screws holding the a/c control head to the dash. Pull that out and inspect the vacuum hoses there. As you move the slide lever to different modes, vacuum is supplied from the control to the hoses you see at the control head rear portion. Also with the glove box liner removed, you can watch the blend door rod move the from max cold to max hot as you rotate the temp. wheel. At the bottom of that servo box are vacuum hoses as well. ck if they are kinked, loose, off etc. You should also be able to watch various vacuum actuators operate as you cylce the mode lever to confirm operation. hopefully you will find a hose as the culprit.

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