1978 NYer Manual A/C Question - Unit will not Cycle from Vent Mode

Later Model C Bodies - "The Formal Years"

  1. Sport Fury 67

    Sport Fury 67 Member

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    I would like any comments on diagnosing an issue with a manual A/C controller for a 1978 NYer. The doors for the ventilation are in the "Vent" mode regardless of the button you select. The temperature setting is working as are all the speeds for the blower, so that should cancel any electrical issues. I am getting a strong vacuum at the end of the hose-line from the engine. I no longer hear any sounds like any of the doors are operating.

    Is it common for the white colored plastic five push button switch block to degrade and crack resulting in a leak so none of the ventilation door actuators stop working?

    I have heard a vacuum leakage sound from the automatic parking brake release when it operates. Does the ventilation and the parking brake use the same vac lines? Is it a concern - possibility?

    Everything worked in all mode when I took it out last. Every month I run the car and cycle through all the ventilation options to keep everything working.Any comments on experiences with this would be appreciated.
     
  2. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    The vac line to the controls is a small one and yes it could be bleeding off all the available vacuum if the leak to the park brake motor is a big one. Try disconnecting that lead and see if your vent doors operate. If not the next likely candidate is the vac control module in the heater control. Try running a dummy vac lead by passing all the controls to the vent motors and see if they operate that way. That helps isolate the problem to a control unit issue. There is a small vac control, usually on the steering column that activates the the park brake release, that could also be leaking.

    Dave
     
  3. BLUPORT

    BLUPORT Loves everyone, except Carmine. FCBO Gold Member

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  4. Sport Fury 67

    Sport Fury 67 Member

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    Thanks for the feedback guys. When I was looking up into the heater box enclosure I noticed the blades of the squirrel cage fan were packed with insulation, leaves, and junk from a rodent that previous made a nest under the hood next to the air intake during it time with the last owner.

    Also the sub-zero weather we experienced a few months back in an un-heated garage is never good for + 40 year old plastic. I will pull the unit out and take a look this weekend.

    How come when I get a few things fixed a few other new ones start giving me issues. One day I will get everything to work....hopefully.....even if it is for an hour.
     
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  5. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Part of the joy of old cars, tear into one thing, find 5 others wrong. Given the car had an infestation problem, the critters for reasons unknown like the taste of rubber hoses and vac line. You can expect to find chew holes is most of the lines so replace them.

    Dave
     
  6. 75LandYacht

    75LandYacht Senior Member FCBO Gold Member

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    Have WE seen pictures of you ride?? If not! Please indulge us with LOTS!!!
     
  7. Sport Fury 67

    Sport Fury 67 Member

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    They are older photos. I will have to create a garage for the site when the weather is nice for photos, also the hose is stored for the winter...

    Drv Side full view.jpg

    Drv Side Interior.jpg

    Engine Bay.jpg

    Eng Compart VIN Plate.jpg

    Pas Side Rear Interior.jpg
     
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  8. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Shit, no hose and the lean burn still works! Nice car.

    Dave
     
  9. Sport Fury 67

    Sport Fury 67 Member

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    Thanks. The Lean Burn works as long as the temps do not go much above 70F. Planning on an Edlebrock upgrade for dependable hot summer drive-ability. Plus the ThermoQuad is leaking gas from the bowl.
     
  10. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Very typical on both counts, even when these cars were new.

    Dave
     
  11. 75LandYacht

    75LandYacht Senior Member FCBO Gold Member

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