Heat Control Valve...good or bad???

[LannyL81]

I have been thinking about removing the heat control valve. My thinking is that it would extend the life of the heater core by having coolant flowing through it all the time instead of just when you want heat.

BUT

Even with the temp slide control put to cool, keeping the door closed to the heater core, will this still let too much heat into the interior?

Would it just be better to have the habit of turning on the heat for a few minutes whenever the car is driven, thereby circulating coolant through the heater core?

Asking now as I have complete access to it since I have the overflow bottle out.

LannyL81

 

[srs244]

in my opinion, YES!!!! you do not want to keep copolant flowing through the system, even with all the controls off. it will get you way too much heat from the radiant heat off the heater core. since you wish to insure circulation, your idea of running the heat for a couple of minutes once a week is a much better idea. as an aside, during the summer, caught in traffic and watching the temp gauge start to climb off the scale, "in the old days" we used to open all the windows (or put the top down) and turn the heater on to high. it was effective enough to provide additional "radiator" surface to keep your cooling system under control until you could get moving again out of traffic. it was an interesting trade off as to whether you wanted to sit by the side of the road and let everythng cool down, or dissipate the heat via the heater (die a bit from the heat), but keep on keeping on so to speak!

 

[Bill75]

My opinion is DON'T remove the heater control valve!!!!!!! The worse thing you want is coolant running thru the core all the time, it'll roast you out in the summer. Somebody at GM decided to eliminate that in my year car, I had to put a shutoff valve in so that I could stand driving the thing. Even with that it's not comfortable on a hot summer day w/o the air on.

Bill

 

[ratflinger]

A related question - Is the valve a normally open or normally closed system?Does the valve require vacuum to open and allow flow or does vacuum close the valve from flow? I just remembered that my vac hose is not connected. Anyone know where it connects to (not on the valve end smartees), just off the top of your heads. I have all the docs needed to research this at home but I'm on the road right now. Thanks in advance.

 

[Sensei]

I believe it is normally open and requires vacuum to close (shut off the heat).

 

[wishuwerehere82]

A simple solution is to put a 2-way ball valve between the water pump and the heater core and a tee fitting where the heater line returns to the intake manifold. That way you can divert the hot water to the manifold when you don't want heat, but keep the water loop flowing. And turn the valve back the other way when you need to get heat.

 

[Bob Chadwick]

A related question - Is the valve a normally open or normally closed system?Does the valve require vacuum to open and allow flow or does vacuum close the valve from flow? I just remembered that my vac hose is not connected. Anyone know where it connects to (not on the valve end smartees), just off the top of your heads. I have all the docs needed to research this at home but I'm on the road right now. Thanks in advance.

It comes through the firewall right behind the distributor.

 

[pgtr]

Yes - as stated above the valve is NO until vac is applied.

It is ONLY closed (vac applied) when the controls are in the OFF position or the MAX AC position.

And sooner or later after the engine is shut off it will open up if closed when last running.

But it gets stranger yet. Some C3 years did NOT have a valve installed from the factory I understand. I want to say 1 or 2 years in the early 70s...??? Anybody?

C3s, (particularly factory AC equipped) are generally held to have a lot of heat problems. It's an opinion I share and a combination of the poor engineering approach of the GM MVAC controls coupled with poor configuration of the C3 ventilation and placement of heater etc... Well at least a good A6 compressor can cool just about anything!

---

On a related note if I may be so bold as to miss the mark and shift this thread in a slightly different direction... if you have a lot of stuff off, open etc. and have experienced 'heat' problems in the insterior - especially in the summer - now might be a good time to look at ways to more positively CLOSE off the heater core per the suggestions above or simply a ball shut off valve or a convoluted vacuum 'relay' solution like I'm toying with presently etc...

 

[Bob Chadwick]

I've got a page with some good information on how all of that stuff works and how you might be able to control the cockpit heat a little better.

 

[Bill75]

But it gets stranger yet. Some C3 years did NOT have a valve installed from the factory I understand. I want to say 1 or 2 years in the early 70s...??? Anybody?

My 75 did not have a valve (stupid!), I had to install a shutoff.

 

[ratflinger]

Bob,

Excellent work!