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Hello all. I am working on a 1968 442 with factory air. I have tracked down all the vacuum lines and hooked them all back up to the correct vacuum pots to get the air to move from floor to vent to defrost. I have a white, vacuum line that is pictured that goes through the firewall to the engine compartment and is open. According to the diagram, is that a vacuum pot that it attaches to somewhere for the AC? And if it is, where would I find that? I don’t see it open vacuum pot in the engine compartment.
Heater control valve, on the passenger rear corner of the intake.
The heate control valve allows coolant to flow thru the heater core until the A/C is put in the MAX position. Then the control head supplied vacuum to the valve causing it to close, stopping the flow of hot coolant thru the heater core.
Heater control valve, on the passenger rear corner of the intake.
The heate control valve allows coolant to flow thru the heater core until the A/C is put in the MAX position. Then the control head supplied vacuum to the valve causing it to close, stopping the flow of hot coolant thru the heater core.
I don’t know how it works on all cars, but on my ‘71 the vacuum turns on and off with the temperature slider. I didn’t check to see what happens on MAX, but it appeared to be the warm / cool slider that controlled the vacuum.
I connected a vacuum gauge to the heater valve vacuum hose on my car and it has no vacuum with the temp slider on WARM and vacuum with the temp slider on COOL
I don’t know how it works on all cars, but on my ‘71 the vacuum turns on and off with the temperature slider. I didn’t check to see what happens on MAX, but it appeared to be the warm / cool slider that controlled the vacuum.
Correct. While the TEMP selector uses a cable to operate the temp blend door in the HVAC box, that lever also operates a vacuum switch that turns the heater control valve off and on. Note that in this application, the heater control valve doesn't control temp. All it does is move between fully open and fully closed. The 1972-earlier A-body cars use a heater control valve that is normally closed and opens when vacuum is applied. The switch on the control head applies vacuum to the valve any time the temp slider is in a position other than fully COLD. Also, the MAX A/C position overrides this vacuum valve and ensures that the heater control valve is closed any time MAX A/C is selected. The point of the heater control valve is to ensure that there is no hot coolant in the heater core to maximize the cooling of the A/C in the cabin.
May 13th, 2024, 04:06 PM
