Only 1" of vacuum to water valve

Fuselage Years

  1. furious70

    furious70 Member

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    Before pulling the heater box for heater core and ac drain leaks I wanted to test operations. Everything but the vacuum to water valve is ok. It's been dead for some time actually. I've got the ash tray and middle vents out so I can see the vacuum regulator off the controls. Is the smaller diameter hose the feed and the green stripped one the out to the water valve? Any tricks to get them loose without breaking off the barbs?
     
  2. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Not sure which car this is?
    Take a box cutter and cut the sides of the hoses where they attach to the barbs if you are going to replace the hoses. There is a vacuum control integral to the heater/AC control unit. It is normally the first item to leak before the vac hoses, so start there. If this is an ATC or ATC II system, they were prone to leak just about every where, so you will have your work cut out for you. It usually is not altogether practical to fix many small leaks, but running a supplementary vacuum pump will usually get you enough vacuum to force the controls to work properly assuming minor leakage is the only defect with the controls.

    Dave
     
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  3. furious70

    furious70 Member

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    70 fury normal ac.
    I assume there are no replacement parts for the vacuum regulator, just the off chance of an nos controller?
     
  4. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    The actual vacuum actuator was usually not serviced, it was replaced. Try www.hiltopautoparts.com, they had these the last time I needed one.

    Dave
     
  5. furious70

    furious70 Member

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    Good call on slitting the hose!

    So I've got no vacuum up to the regulator on the side of the controller. The line to the regulator is teed off and also feeds the time delay relay and maybe the fresh air actuator?
    Any ideas on why the controller would be 'dead' on just that one port (flappers move correctly)? Easiest fix is to just plumb vacuum to the teed line and bypass the controller?
     
  6. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Check the vacuum switch (delay module) on the center front of the air box inside the engine bay. There are several vacuum hoses hooked to it, check them for leaks. The module itself has a small piston inside that is sometimes blown out of the housing by an engine fart back thru the carb resulting in a leak and a dead module. If my brain is still working, the delay module feeds part of the controls under the dash. The FSM should have the vacuum routing to verify this. Shade tree mechanics sometimes start screwing with rerouting the control hoses when they have problems with the control. This can make diagnostics a lot more challenging so verify your hose routing before you do anything else.

    Dave
     
  7. furious70

    furious70 Member

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    I get what you're saying but isn't the delay module fed vacuum from the control module not vice versa? There's one smaller diameter vac hose under the hood that feeds the control module in the dash. My delay relay is still oem routed.
     
  8. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    You are correct about the feed, I was thinking a large leak at the delay module would disable the regulated vacuum pathway to the heater water control valve. The white plastic vacuum control inside the heater control unit is probably defective if the delay unit is intact or the vacuum control on the slider could be bad. I sent you a vacuum diagram on a PM.

    Dave
     
  9. furious70

    furious70 Member

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    Ya, got the diagram, matches my fsm. I don't have vacuum coming out of the controller port (3 or 4 it's hard to tell how the ports are numbered) that then tees off to the slider and delay module