Hot air blowing in air ducts

[jkh290]

My wife and I took a ride in 64 Linc convert yesterday. It was a nice day to enjoy a ride. After driving for a while it became warm driving. I have a temp gauge clipped to one of the air vents. I had the heat off and a/c off, but could still feel warm air coming through the vent's, the temp gauge stuck on the air vent read around 120 degrees. Any suggestions on where to start looking? I'm feeling that one of the air duct's is stuck open and allowing warm air in the the cabin, not sure if I can take to a local A/C shop? The a/c blows cold when first starting but after the engine warms up, it's not as cold as it was. Not sure if this is something that a modern A/C shop can look at, or if this is something an old timer needs to resolve. Looking in the service manual get's over my pay grade to try and figure out.

Any suggestions would be appreciated.

Jim

[JimA]

Jim,

The first, and easiest, thing I would check is the control valve on the heater hose. See if it moves when controls are moved from heat to off. If it doesn't move, look somewhere else for the problem. Even if it moves, it might not be closing completely.

You can get a feel if it's closing completely by doing a cold start with HVAC off and see if both the supply and return hoses are hot. The return should be much less hot than the supply if the valve is working.

If there's not much difference in the temps of the two hoses, you can also test to see if it's working by clamping off the supply hose with vice grips or some other clamping device. If the air temp at the vents cools pretty quickly, or doesn't get hot, the valve isn't closing.

Close the hood when you're testing the control valve so the hot engine air isn't sucked in thru the cowl intake.

Jim

[Suicidekid63]

definitely sounds like bad heater control valve or rotted vacuum lines going to it. I had the same issue years ago on my '63 and a new valve fixed the problem.
1963 valve is vacuum = open valve
I think Rock Auto has them, but if not I just purchased a non stock one from ebay and it worked fine. Much cheaper than the usuals (Baker's, Lincolnland, etc)

[Dan Szwarc]

Sounds like a rotted heater valve. It's leaking internally and not staying closed.

[jkh290]

Thank you for the info, I will check out the control valve

[bd94s10]

Did you get this resolved?

Checkout my post on July 15 2018 here https://www.thelincolnforum.net/phpbb3/ ... ot#p394028 which I tie into the below thread that helped me when I had the issue. I changed the heater control valve and it resolved the issue.

https://www.thelincolnforum.net/phpbb3/ ... ot#p366049

Good luck. It is not too tough to change out under the hood.