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I apologize in advance if this has already been discussed on here, but I was unable to find what I was looking for. Anyways, I am the third owner of a 1974 F-250 with a 390, and factory A/C. Surprisingly, the compressor is in good shape along with all of the other components of the A/C. I am, however, missing the heater control valve. I know that these things are pretty easy to find online, but in looking up specs on my truck, I cannot find the heater control valve that has dual ports for vacuum hoses. The common question I get at my local shops/parts store is "are you sure that both lines run to the control valve." Yes I am sure and I have even found spec sheets that show a control valve with two vacuum hoses running to it.
Does anyone have any idea if these are still made or if there is some modification that I need to do in order to use a control valve with one vacuum hose port?
I have also attached the specs I have found online.
I think that system uses a temp control cable to mix heat and cold with the blend door. So the 2 lines on the HCV would only be used to cut off the hot water in the MAX-AIR position.
Not sure why they would have chose 2 lines when most of their system used one, but engineers do wierd things. there is a vacuum valve connected to the temp lever in the dash control that regulates those 2 lines, so you could test to see which one has vacuum at MAX-AIR and use a single hose HCV that is normally open.
also if non of that works, you could just use a manual shut off valve for the heater hose and just shut it off on those extremely hot days. I live on Cape Cod, if it was mine it would never have to be shut off, our hottest days are in the 80-'s
D4AZ-18495-A (replaced C9AZ-18495-B & D1AZ-18495-B) .. Vacuum Controlled Heater Water Valve - Use with factory installed integral A/C (Motorcraft YG-136) / Available from Ford & auto parts stores.
There are no cables used with factory installed integral A/C. The entire system is operated by a vacuum controlled selector valve assy., vacuum operated blend door motors and heater water valve.
D4AZ-18495-A (replaced C9AZ-18495-B & D1AZ-18495-B) .. Vacuum Controlled Heater Water Valve - Use with factory installed integral A/C (Motorcraft YG-136) / Available from Ford & auto parts stores.
There are no cables used with factory installed integral A/C. The entire system is operated by a vacuum controlled selector valve assy., vacuum operated blend door motors and heater water valve.
1973/75 F100/350:
In your diagram, that 18518 I believe is the temperature blend door cable. The vacuum control valve controls all the dampers except the temp blend door. The cable controls the temp. If the truck had automatic temp control, it would have an aspirator under the dash that was controlled by a cable, then the aspirator would supply vacuum to the temp door servo, but I don't think they ever put that system in a pickup back then.
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