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Hi everyone! I have a 72 cutlass with a 350 and AC. So I've included some photos of the NOS heater control valve I bought today. It has the base that screws onto the manifold, the vacuum nipple, and the heater hose attachment point. However, there is another part that's shown in the second photo that is threaded on the inside diameter. Is this the wrong part or am I missing something. I don't seem to have anything that would connect to this.
Thanls!
chris
Last edited by Oldssupreme; November 22nd, 2017 at 03:24 PM.
May I also ask if the one in the photo in the first post is correct for my 72 350 with AC? The one I have on now has a lever connected to the vacuum sort of like in the attached photo above. But I'm not sure if that was replaced or original. Thanks!
May I also ask if the one in the photo in the first post is correct for my 72 350 with AC? The one I have on now has a lever connected to the vacuum sort of like in the attached photo above. But I'm not sure if that was replaced or original. Thanks!
This lever-actuated valve is for a Buick. Olds used a valve that screws into the intake manifold.
Ok thanks Joe. So the one in the photo above with the pink ribbon which is the one currently on my car was probably a replacement before I got the car?
Ok thanks Joe. So the one in the photo above with the pink ribbon which is the one currently on my car was probably a replacement before I got the car?
Note that this valve has a pipe thread fitting to screw into the intake. The Buick valve you posted previously has two hose barbs and goes inline in the heater hose. In any case, Oldsmobile typically used a valve like the one in your first photo. The correct P/N for your car is 411822, which is a normally closed valve that opens when vacuum is applied.
I think many people switched to that type valve with a lever and detached vacuum canister as they don't leak coolant if the vacuum diaphragm fails. The Olds style valve will leak coolant if the diaphragm fails. That irritated me to no end back in the 80s-90s when I was daily driving my Cutlass to school and work.
I think many people switched to that type valve with a lever and detached vacuum canister as they don't leak coolant if the vacuum diaphragm fails. The Olds style valve will leak coolant if the diaphragm fails. That irritated me to no end back in the 80s-90s when I was daily driving my Cutlass to school and work.
I'll second this. In fact, I got so tired of replacing the leaking valves on my 84 Custom Cruiser that I put in a nipple and used a plastic Chevy style heater control valve. The Chevy valve has the external vacuum actuator, the plastic doesn't corrode, and since it's inline in the hose it's very easy to replace. Of course, that was a normally open style and won't work on the 72-earlier A-body cars.
So if you both had issues with these type leaking, then maybe I should just keep the current one in. I had planned on replacing it for aesthetic reasons (the current one is not leaking).
Chris
So if you both had issues with these type leaking, then maybe I should just keep the current one in. I had planned on replacing it for aesthetic reasons (the current one is not leaking).
Chris
In fairness, the ones I've had trouble with are the made-in-Mexico aftermarket ones from Four Seasons (and even a new ACDelco from the dealership - also made in Mexico ).
I don't remember the brand this one is. I'll have to look at the box. But if it's NOS, does the rubber diaphragm break down over time even if it's not being used?
I have the same valve on the shelf for my car.
It is stamped with:
TYPE H25
RANCO
COLO, USA
The backside has an ink label:
H25-124
The valve is normally open and takes vacuum to close.
Just today I was working on the car, changing the heater core and I'll install the new heater valve tomorrow. I connected a vacuum gauge to the heater valve vacuum hose on my car and it has no vacuum with the temp slider on WARM and vacuum with the temp slider on COOL, so this valve matches my car's vacuum operation.
I recommend you check the vacuum operation on your '72 to ensure it matches your heater valve as my '71 operates opposite of what the factory manual describes per Joe's posts.
Last edited by Fun71; November 25th, 2017 at 05:56 PM.
I have been looking for answers on my heater valve and happen to stumble on this old thread and was hoping someone would read this and have an answer. It's frustrating to know something exists but can't get your hands on one. Kind of like Big
foot. I have a '75 Delta Convertible and am replacing the heater valve. My valve has a screw in heat switch. Does anyone know what the technical name is and where I can get my hands on one? Thanks for your participation.
It's called a thermal or low blower range relay. Its function is to allow low speed blower operation when the HVAC control is in OFF and coolant temp is 120° or higher.
From 1974 CSM. 1975 will be similar. It was eliminated for 1976.
I honestly don't know where you'd find one short of an old stock or junkyard piece. I couldn't get a good part number from my Nov 73 parts book and I don't know if aftermarket ever supported it.
Worst to worst, if you can't find one, and not having it interferes with blower operation, leave it unplugged and install a jumper across the brown wires in the plug.
P/N 6490448 Switch, Thermal Blower (Group 9.275). Used on 1973 cars with automatic A/C (second design with two terminals) and all 74-75 cars with auto A/C. There's at least one on ebay right now for $10. As Glenn noted, there's nothing magic about this. Despite being called a "relay", it's just a thermally operated switch that closes when coolant temp reaches 120 deg F. This provides power to the blower motor so that the auto system isn't blowing cold air if you turn the heat on before the engine is warmed up. The 1971-older cars with auto A/C didn't use it either. The 1971-72 and first design 1973 cars used a one-terminal version that grounded through the switch body.
Thanks Joe, I should be getting my 350 back from the shop in a couple of weeks and I'm trying to wrap up a few loose ends. I can now check this off my list.
You da man. I ended up finding one earlier on ebay and they wanted $40. I think I'll order the one you found. Now I can afford a new pair of fuzzy dice for the mirror.
November 22nd, 2017, 01:12 PM
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