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How To ? Convert Heater Vacuum Control to Electric

jndyer on Thu January 14, 2010 5:51 PM User is offline

Year: 1981
Engine Size: 350
Country of Origin: United States

I have a 1981 Corvette with fully functioning stock A/C. For reasons to lengthy to discuss, I want to convert (or modify) the Heater A/C Control from vacuum actuated to electric. Is this possible, and if so, is it possible with limited parts replacement and a small brain? I understand I would need a modern electric heater control panel assembly. Thanks in advance for any help, as I may be the forum's village idiot. J.D.

tony1963 on Thu January 14, 2010 7:30 PM User is offline

This is not a practical undertaking. The entire system is designed to be electronically controlled, blend doors, etc. There are also sensors to keep the unit from freezing and it is typically tied to the engine computer, too.

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mk378 on Fri January 15, 2010 10:17 AM User is offline

An electric vacuum pump could be fitted to run the system instead of vacuum from the engine.

jndyer on Fri January 15, 2010 2:20 PM User is offline

Thx for the replies. If an electric vacuum pump can be used, where would one obtain said pump? And, what kind of control panel would be used? In a nutshell, the motor is 500 HP and there is little to no vacuum available. I am converting the headlight and wiper systems to electric, and would like to do so with the heater controls. Additionally, I am custom fabricating a replacement console and gauge cluster, and trying to relocate the A/C-Heater Control panel and stereo to the glove box compartment. So, that's what I'm up to. Any additional info is greatly appreciated. Again, thx in advance. J.D.

bohica2xo on Fri January 15, 2010 3:24 PM User is offline

There have been several alternators made with vacuum pumps. Delco & Hitachi put them on the back, Nippondenso runs the vac pump on the front behind the pulley.

Many of the eurotrash diesel cars have vacuum pumps. Probably the most straightforeward solution, just replace the alternator. There should be an alternator that will work. The little Denso hairpin puts out about twice what your OEM alternator puts out, and is smaller.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Sat January 16, 2010 10:04 AM User is offline

I am converting the headlight and wiper systems to electric, and would like to do so with the heater controls.

Let me recall some history, wipers were first vacuum operated in the 20's to 50's, go up a slight incline and the wipers would stop, was in the late 40's that came out with an engine mounted fuel pump with a second diaphragm for a vacuum boost. But went all electric in the mid 50's, you still have vacuum operated wipers in your 81?

Here is one from a 1950 GMC truck, can still buy them but not a couple of bucks anymore.

Getting back to basics, but not knowing what you did, are you still using carbs on your engine? Still using the HEI with vacuum advance? That's intake vacuum and not knowing what you did to your engine sure that vacuum also has gone to hell. One option is to use venturi vacuum if you still have carbs on this thing, venturi vacuum is always strong. Can even add one by drilling a #60 drill hole above the throttle vane with a tube on the outside to hook your heater hose to it. Need a canister and a check valve, these vacuum operated heater actuators don't draw that much and only require about 7"/Hg of vacuum to operate effectively. I think your heater control is very similar to my 82 Chevy motor home, just three actuators for vent control, lower, dash, and defrosters. Operate in the no-go mode, either full on or full off. My 88 Supra uses electric actuators because with an intake going up to 15 psi positive pressure, not very much vacuum. Headlamp lids are also electric if you are looking for a parts source.

In like my 82 Chevy motorhome, that slide switch operates a vacuum switch, had to take that all apart and clean it, but could make a cam and install micro switches to emulate the same closure with electric actuators if I wanted to. I assume your heater control is a heater water valve, that can remain like it is, you don't mention if you have AC.

So the question is, to either obtain a vacuum or to modify your system. Airplanes of the 30's - 50's used a vacuum operated gyro compress, was like a dual cone mounted to the side of the plane with a tiny orifice drilled in the side, whenever you have mass air flow past that orifice, you will have a vacuum. Those joke like AC air compressor operated vacuum pumps work on that same principle, normally a tiny tube pointed in the direction of the air flow. Never tried this, but bet installing a tube in your exhaust pipe would work with enough copper tube so the rubber hose attached to it doesn't melt.

Tell us what you got, has to be an easy solution, always is.

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