Vacuum-only heat controls?

Jeff Erwin

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I am in the process of removing my instrument cluster (71 Superbee) to replace lights, put an original tach in, replace other instruments, fix the heater controls etc.

I removed the radio (hopeless to fix) and pulled the heater controls. This was originally a 383 with air car, not sure what is original and what else was replaced in the heater system.

I was kinda taken back when I saw that the heater controls were completely vacuum operated. No control cables in the controls or the heater box, just vacuum actuators. There is a coil of vacuum hoses (small diameter) neatly coiled on the passenger side firewall engine side where they enter the firewall.

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Questions:
1. I didn't realize they offered a 100% vacuum operated heater system in 71, the shop manuals all talk about control cables. Is this original to 71 or are the controls and heater box from another year?
2. I need a vacuum source in the engine to supply the two vacuum lines that seem to power the whole thing. I can't use the nipple coming from the metering block in the center carb, it is for the vacuum advance and the pressure changes with the engine speed (obviously). There is a larger vacuum hose connected to the base of the center carb that goes to the power steering, then returns to a nipple at the back of the intake manifold. Can I tap into that? Where else can I find full vacuum to power this thing?
3. What are the two vacuum lines in the engine compartment for? I read something about a 'vacuum controlled water shutoff valve', is one of these for that? Do I need that? Can I just hook both lines to a vacuum source, assuming I find one?
4. Is there any way to test the heater box without pulling it? I suspect it is fine, all looks intact and the heater core works, I can feel hot air coming from the dash vents. The controls are dead, no vacuum source.

I'm sure I will have more questions as I go, getting answers to these would be a great help!
 

Roger63

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I will try
1. There is a vacuum heater valve that mounts to the passenger fender well.
2. Mine has a vacuum canister that supplied via the intake or base of the carburetor.
3. The 2 vacuum lines that run into cabin are vacuum supply to the system from the reservoir (larger line) the other connects to the temperature control valve.
I will get a picture shortly so ya know what your looking for.
 

bee71

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I am in the process of removing my instrument cluster (71 Superbee) to replace lights, put an original tach in, replace other instruments, fix the heater controls etc.

I removed the radio (hopeless to fix) and pulled the heater controls. This was originally a 383 with air car, not sure what is original and what else was replaced in the heater system.

I was kinda taken back when I saw that the heater controls were completely vacuum operated. No control cables in the controls or the heater box, just vacuum actuators. There is a coil of vacuum hoses (small diameter) neatly coiled on the passenger side firewall engine side where they enter the firewall.

View attachment 1172158 View attachment 1172159 View attachment 1172160
Questions:
1. I didn't realize they offered a 100% vacuum operated heater system in 71, the shop manuals all talk about control cables. Is this original to 71 or are the controls and heater box from another year?
2. I need a vacuum source in the engine to supply the two vacuum lines that seem to power the whole thing. I can't use the nipple coming from the metering block in the center carb, it is for the vacuum advance and the pressure changes with the engine speed (obviously). There is a larger vacuum hose connected to the base of the center carb that goes to the power steering, then returns to a nipple at the back of the intake manifold. Can I tap into that? Where else can I find full vacuum to power this thing?
3. What are the two vacuum lines in the engine compartment for? I read something about a 'vacuum controlled water shutoff valve', is one of these for that? Do I need that? Can I just hook both lines to a vacuum source, assuming I find one?
4. Is there any way to test the heater box without pulling it? I suspect it is fine, all looks intact and the heater core works, I can feel hot air coming from the dash vents. The controls are dead, no vacuum source.

I'm sure I will have more questions as I go, getting answers to these would be a great help!
 

bee71

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You have a broken nipple on the plastic control box. Look at the square vacuum plug connecter it might be in there.
 

Jeff Erwin

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You have a broken nipple on the plastic control box. Look at the square vacuum plug connecter it might be in there.
Just a light trick. All 7 nipples are there, cluster of 5 and set of two.
 

Roger63

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sorry about the delay I got sidetracked
 

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