Vacuum operated heat control - where do I connect it to?

[Brett James-McCall]

Hi,
Need help from you knowledgable chaps. I have a vacuum operated heat control like this one: Heater Control Valve Vacuum Operated - Heater Valves & Cables

Can someone tell me where I should connect this to. I assume on the carb somewhere? I am running a Holley Street Avenger. Thanks

Brett

 

[Ron Earp]

That looks like what it says, a vacuum operated heater control valve. If I am not mistaken that unit uses vacuum from your HVAC system to let hot water in the heater core. I was looking at one the other day because my Torino has a vacuum operated HVAC system and has a few similar valves and actuators.

I don't think it has anything to do with your carb except that the "master tap" for the vacuum system might come off somewhere near your carb. If you hooked it directly to your carb then it'd always be open when the engine was running and hot water would circulate through your heater core.

If your goal is to regulate water through your heater core, and you don't have a vacuum powered HVAC system, then you'd be better off using a simple cable operated heater control valve.

 

[Brett James-McCall]

Ron,
I also have one of these: Vacuum Actuator Solenoid - Vacuum Accessories

My assumption is that the solenoid opens to allow the vacuum when the switch is turned on?

Brett

 

[Paul W]

The big valve is to cut the hot coolant flowing through the heater core when you are using the ac. You can either mount it in the engine bay after the water hose comes off the inlet manifold (behind the thermostat) or in the same hose where it appears at the heater matrix. The vacum hose only needs to be a tiny bore but does need permanant vac - same as the brake boosters. The switch you have controls the vac i.e. when the heater mode is anything but heat the water flow stops through the core.
That said my valve stopped functioning after a year or so and after speaking to others that had the same issue, I fitted a manual valve that to be honest very rarely gets opened. Also means you don't need to have vac lines etc.

 

[Brett James-McCall]

Paul, which controls did you use on yours again? The sliders or the rotary type? I have the ones that came with 3 rotary switches.

I assume you would just manually open the valve if you needed heat as well as changing the switch location?

Also, where di you get you valve from. Thanks

Brett

 

[Paul W]

I have the rotary style controls on my dash - all the valves etc came in the ac kit.
The valve I have now is a standard chromed 15mm plumbing type valve - the type you use a flatblade screwdriver to turn on and off. Yes I just open the valve if I need a bit of heat - this is a rare occasion in my car though.

 

[Phil]

Brett:
The vacuum controls work pretty good, but you may need to put a small accumulator with a check valve in line somewhere to prevent the controls from cycling during various throttle openings and changing vacuum.
I had a vehicle with vacuum controls and the default setting was defrost air, when going up a long hill with floor heat set on the control the unit would switch to defrost, then back to the floor setting when the throttle was closed or close to it on the level.
A small in line canister usually solves this. Otherwise everything worked well.
Cheers
Phil