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1952 Mercury Vaccum Operated Heater

My 52 Mercury Heater fan is working now, but the air blowing out of it is not warm and this dose not change when I moving the temp lever on the dash. Is it likely just the heater control valve or is there something else possible wrong?

I’m not finding anything online about how these systems work and my shop manual doesn’t give me much info.

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Can you feel hot water circulating in the heater hoses? The heater core could be plugged.

I’ll have to check this tomorrow. Which hose should the vacuum control be in the middle of in the engine compartment - I’m assuming top because the hot coolant rises? and that’s where it needs to control how much hot coolant flows through the heater core - or do I not understand this correctly?

I really don’t think they used water shut off valves back in 1952. I believe the hot water just goes into the heater core and the piano wire control just shuts or opens the door to let heat inside. On the Ford trucks there was even a manual door on the passenger side to reach down and open or close. No vacuum controls at all. Agree either the heater core is plugged or the wire came off the door. I think.
On my 59 Pontiac I had to actually put a clamp on the heater hoses in the summer to shut the heat off. There was no water shut off even in 59. Of course that was GM but can’t believe Ford would have been that far ahead of the curve.

On my 70’s Ford truck it is very easy to just pop the hood and see where the heater control cable activates the valve which allows hot coolant into the heater core. Have someone in the drivers seat operate the control while you look in the engine compartment. I hadn’t operated that valve in some years and last winter I wanted to use it, and it was frozen in the “no-heat” position. I had to clean and lube the cable and valve mechanism to get it working again.

Some caution is in order here. If the valve hasn’t been operated in a long time, it’s possible there’s a hidden leak, and when it opens up the first time you’ll find you got a boatload of coolant pouring into the passenger compartment.

If there’s a valve that would be my fist guess as a problem.

Maybe one of these
is in one of the heater hoses

If my memory is correct, the 1952 Mercury has lever type heater controls mounted on a horizontal panel under the steering column much like controls in am airplane. I am almost certain that one lever says something like Temp. Have someone move this lever while you look under the hood. I believe you will find the heat control valve. This assumes your Mercury has rhe factory installed heater. The heater was an option in those days. I am almost certain that the heat valve was manually operated and not vacuum controlled.

Again this is for the 58 Ford, but since the motor was essentially the same, there is a good chance the rest of the system is pretty close too. The 58 did have some vacuum controls so if you think yours does too, then the information here should help you sort it out.

There are heater control valves for '52 Fords and Mercuries on Ebay, with a vacuum port on top.

Well I certainly could be mistaken and they could be more advanced than I thought. Rockauto has both the parts manual and repair manual available while stock lasts. Even at my age I can’t hardly recall stuff older than 59. First thing I’d do if I owned one is to try and get as much of the factory information as I could for reference.

I am happy to announce the heater is working, but I didn’t really do anything. I did operate the temp control handle back and forth few times and then just left it on high for awhile. I had the car out for a ride after work today and about an hour into driving I could feel heat starting to come from the direction of the heater core so I turned the fan on and sure enough - warmth!

How this heater must work is that the cable runs from under that dash to the shroud around the heater core inside the car where there is a valve (?) of some kind that moves when the cable is operated. There is a hose running from this assembly to the engine compartment where there is a heater valve that must be vacuum controlled. I did put this vacuum control in several years ago - I think to replaced the old one that was there. The outside of the control is kind of dirty and I’m guessing it was maybe stuck from not being used and then just came loose somehow. I think the vacuum is created by the intake manifold, but I’ll need to investigate more on that.

Hopefully the heater keeps working - it was nice end to the ride on a rather chilly day here in MN.

Thanks for the interesting feedback. I see the photo in @texases post above of a vacuum operated valve of some type. This seems sort of overkill for the heater coolant control valve, but maybe it made sense in 1952 … lol …

You post reminds me OP of a problem I had with my early 70’s Ford truck a while back. The throttle control/accelerator pump linkage wasn’t working for some reason. I wasn’t getting a good shot of gas like I use to, when I stepped on the pedal. So I inquired here, took that info w/me to inspect the linkage at the carb carefully. Not sure about your 52, but inspecting the carb is an awkward thing on a Ford truck, the engine compartment is quite large and the carb sits at the very top. But somehow with the aid of a step ladder and a piece of foam rubber to lean against, I managed to situate myself so I could see that linkage as I operated the throttle. For the life me I couldn’t figure out how it was supposed to work, but it clearly wasn’t working.

Finally I gave up, thought I’d just remove the carb so I could figure out on the bench. But I had to drive the truck in the meantime, and the nest time I used it, lo and behold, the accelerator pump started working perfectly. And has never failed since.

What part of Minnesota if I may ask? I’m in southern MN.

Central, MN

Isn’t that the way it goes sometime!? The vacuum operated valve pictured above is what I have in the car engine compartment. When I looked at it yesterday I noticed that it is in the lower hose coming out of the heater core, but that hose is connected to the water pump so maybe it is correct? For now I’m going to assume that the valve was stuck and came loose somehow.