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Hot water control valve question

Jeff Erwin

FBBO Gold Member
FBBO Gold Member
Local time
5:49 PM
Jun 19, 2021
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Woodinville, WA
71 Charger, originally AC car, AC long gone. Still has the AC heater box and controls. I've been putting the vacuum system back together so I get air to the right place. Heater worked great but only blew through dash vents. All is working now, heat goes to the right vents. Now adding the water control valve that is controlled by the COLD/HOT lever which regulates the amount of vacuum to the valve under the hood.

I found a NOS valve, pic below. The question I have is regarding the hose sizes. The hose connectors from the water pump to the valve, then to the connection on the firewall are slightly smaller than the return side, which makes no sense. The current hoses from the water pump to the firewall and back are the same size. This means, I think, that the hose connection on the water pump pressure side is going to be larger than the connection on the valve. Shouldn't all the hose connections on the water valve be the same size?

Screenshot 2022-12-05 at 10.04.00 AM.png
No. They are different on the a/c valve. Hose from thermostat is normally the in side to the heater core. The out side from the core runs to the water pump.. Thermo stat side nipple (1/2") is smaller than the water pump nipple. (5/8") Flow runs from into the left heater core fitting and out the right fitting..