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Daves55Sedan · 05-01-2012, 11:45 PM

Yeah, you have got the vacuum operated heater control valve. That must have been a late '55. It was the standard control for the '56 model. My '55 has the mechanical control valve.
But, heres what you need. One hose runs from the thermostat valve on the intake manifiold to the heater control valve located in the heater plenum. Another hose runs from the heater control valve in the plenum to a plastic Tee fitting under the dash. The 2nd port of the Tee has a hose that runs thru the firewall and connects to the manifold vacuum line. The 3rd port of the Tee has a hose that connects to the vacuum wiper motor.
Since you have electric wipers now, you can eliminate the Tee altogether and run a new hose from the manifold vacuum line directly to the heater control valve in the heater plenum. You should notice a round cutout at the top of the cardboard heater register for the rubber hose to run thru.
The control valve itself can be rebuilt if it is not operating. (If you have heat coming out of the register in the summer when the valve is shut off via the mechanical cable to the heater control), is a good sign that it needs repair.
Concours parts does rebuild them, but it is very expensive.

05-01-2012, 11:45 PM	#2
Daves55Sedan Senior Member Join Date: May 2010 Location: Granite City, Illinois Posts: 3,008	Re: 55 Heater Box switch Yeah, you have got the vacuum operated heater control valve. That must have been a late '55. It was the standard control for the '56 model. My '55 has the mechanical control valve. But, heres what you need. One hose runs from the thermostat valve on the intake manifiold to the heater control valve located in the heater plenum. Another hose runs from the heater control valve in the plenum to a plastic Tee fitting under the dash. The 2nd port of the Tee has a hose that runs thru the firewall and connects to the manifold vacuum line. The 3rd port of the Tee has a hose that connects to the vacuum wiper motor. Since you have electric wipers now, you can eliminate the Tee altogether and run a new hose from the manifold vacuum line directly to the heater control valve in the heater plenum. You should notice a round cutout at the top of the cardboard heater register for the rubber hose to run thru. The control valve itself can be rebuilt if it is not operating. (If you have heat coming out of the register in the summer when the valve is shut off via the mechanical cable to the heater control), is a good sign that it needs repair. Concours parts does rebuild them, but it is very expensive.