1976 Seville climate control help please ...
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 1976 Seville climate control help please ... in Past Cadillac Vehicle Discussion; Hi everyone, I'm not on here much (sm. biz owner), so I appreciate any help I can get. Thanks in ...
  1. #1
    mduclow is offline Cadillac Owners Member
    Automobile(s): 1976 Seville
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    1976 Seville climate control help please ...

    Hi everyone, I'm not on here much (sm. biz owner), so I appreciate any help I can get. Thanks in advance.

    I could use some help with the climate control on a 1976 Seville with a well massaged 454 chevy, low vacuum (enough to run the brake booster). I have it all connected properly (as best I can tell), but the controls give an unexpected output. If I want heat, I have to go to a cold temp, and then heat will come out the vents. It's impossible to get it out the lower vents unless I set the temp to 85 or so but then it's cold, not hot. The doors do seem to set the proper output (upper-vents/lower-vents), but the temp is way out of whack, almost reversed.

    I really don't know anything about these climate controls, I do have the shop & body manual for the car, but it is a very complicated system to the novice, and I am at a bit of a loss in turning all that info into a solution to my problem.

    If anyone could help me get started on chasing this down, I'd be very grateful.

    Marc

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 1976 Seville climate control help please ...

    I'd start by looking for a vacuum leak.

    P.S.
    Does the parking brake release when you put the car in gear? It's vacuum operated and on the same vacuum circuit.

  4. #3
    mduclow is offline Cadillac Owners Member
    Automobile(s): 1976 Seville
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    Re: 1976 Seville climate control help please ...

    Thank you for the response and help!

    Well, at manifold vacuum (carb base-plate) it is pulling 10-11 in/hg, at the cruise control it is pulling 12 in/hg. This is enough to run the power brake booster, but is it enough to run the climate control properly? As mentioned it does seem to run the doors properly, but the temp is all out of whack in relation to the dial setting the temp.

    I do believe the e-brake is releasing with the shift lever, but I'll re-check that to be sure.

  5. #4
    mduclow is offline Cadillac Owners Member
    Automobile(s): 1976 Seville
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    Re: 1976 Seville climate control help please ...

    OK, I checked the parking brake and it does in fact release with the shift lever

    So, where do we go from here? Thanks again for any help you can offer!

    Marc

  6. #5
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 1976 Seville climate control help please ...

    I'd study the manual and check the vacuum control system. Sounds like you may have a cracked (leaky) vacuum line or one that is broken off and disconnected. It is after all, 37 years old.

  7. #6
    cadillac_al is offline Cadillac Owners Connoisseur
    Automobile(s): Cadillac 78 Seville, 78 Coupe de Ville, 92 Sedan de Ville
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    Re: 1976 Seville climate control help please ...

    I'm afraid your only help is going to come from that FSM. I have never mastered this system and mine was bypassed before I bought the car 15 years ago. Mine has a basic ball valve replacing the heater valve (manual operation) and a push button for high blower. It's primitive but it gets me by. I wonder if the vacuum is strong enough to move the doors but maybe not strong enough to activate the heater valve? I'm just thinking out loud and guessing.

    I do have a fair amount of 76 Seville parts for sale if you need other parts (blue interior). I was planning on putting the climate control in my 78 Seville someday, but we all know someday never comes. I am in the process of selling my 78 Seville and hate to part with the climate control at this point in case a future buyers decision hinges on that climate control. Good luck.

  8. #7
    mduclow is offline Cadillac Owners Member
    Automobile(s): 1976 Seville
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    Re: 1976 Seville climate control help please ...

    Thank you for the suggestions, as I 'sort of' expected I need to start with the vacuum part of the system and make sure everything is proper. I will start chasing down each of the vacuum lines to confirm A) they are properly hooked up, and B) that they are in good working order

    I will post back when I have had a chance to go over it all, then hopefully we can move on to the next thing to tackle if it all seems good. The manual will help me if I know where to start, and this gives me a great starting point.

    I'd really love to have the climate control working properly on this car, it's really a nice one. The car is all original except for the drivetrain and suspension modifications, all the trim is original and the car only has 43,000 original miles. It was painted, original color, about 23 years ago and still looks very nice. It has almost never been in rain and never in snow/salt that I know of. Maybe a little when new, but it sure doesn't look like it, and I've been all over this car, having pulled the motor for service twice since I owned it and done most of the suspension mods myself.

    Marc

    P.S. Does anyone think it's worth seeing a dealer about this? Or is that just asking for a big bill and a lot of "Well, there's not enough vacuum, you're going to have to fix that first..." ?

  9. #8
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 1976 Seville climate control help please ...

    Since you have a FSM and seem to have a basic mechanical aptitude, I'd avoid the dealer. Fist off you definitely will be asking for (and getting) a big bill. Secondly that car is probably older than most of their mechanics and I'd bet that the majority of them probably know less about that system and how it operates than we do and have most likely never even seen an HVAC system like that. I can just see then all standing around it now.

  10. #9
    mduclow is offline Cadillac Owners Member
    Automobile(s): 1976 Seville
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    Re: 1976 Seville climate control help please ...

    That is probably true about the dealer!

    Ok, maybe I can get some time soon to start tracing all of those vacuum lines, we'll get those confirmed good and see where we are at. One thing I can say about the vacuum, the line from the engine bay (main feed line) was not connected when I first got the car, everything blew out the upper vents, now at least the vents seem to do the correct thing based on the dial selections. Don't know if that little nugget of info is helpful to anyone, thought I'd mention it.

    Thanks for the support and help, it is greatly appreciated.

    Marc

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