Heater by-pass valve

[77-4speed]

Hello all,

Bobchad was helping me with this problem but I just want to make sure. I want to put in a by-pass valve so that the hot engine coolant will not flow through the heater core. I know there are a lot of C3 owners out there who have made this modification in the constant battle of interior heat. Could anyone post a picture of either:

1) your engine with the heater by-pass valve installed so I can identify the correct hose to cut into

2) your engine with the above mentioned hose pointed out

I would really appreciate your help on this.

Sincerely,

Russ Fulks

 

[69MyWay]

Look at your engine. Locate the main upper radiator hose on the front of the intake manifold. Look just back to the passenger side and you will see a heater hose coming out of the intake manifold. This will be about 5/8" hose. Follow it back to the firewall. Make sure you don't already have a valve in the car that has just gone bad, or the vacuum line came off.

Take you manual shut off valve if that is what you desire, and eyeball the best area for your application for it to sit in the heater hose. Usually, the closer to the firewall the better. Cut the hose, install the valve, and clamp it all back. Top off the coolant and you are done.

 

[77-4speed]

Chris,

There is the factory valve on the hose. The vacuum line is attached although I haven't tested it for vacuum as doing so would require permanent removal of the line. It was my understanding that this valve is normaly open and only closes the flow to the heater core when the A/C is turned on.

When I turn the A/C on (which is infrequent) the heat problem stops.

Is my understanding incorrect?

-Russ

btw: just in case anybody didn't figure it out by my name, it's a 77 4-speed

 

[69MyWay]

Yep, I can't remember if that valve needs vacuum to close, or closes when the vacuum is removed.

You can play with it a tad.


#1, pull the vacuum line off and plug the line with a small say #10 screw. Check to see if heat stops on the other side of the hose.

#2, plug the line, then run a splitter T over to a vacuum port on the intake. Thus, as long as the engine is running, the valve will stay closed and you don't have to cut any hoses!

By testing it with the vacuum line on and off, you will know pretty quick which way to rig it.

Also, you can simply start the car with the a/c off, pull the vacuum line off and feel for vacuum, then turn the a/c on, and feel for vacuum. In either event, you want to duplicate the a/c on vacuum signal to the valve to keep the heater turned off.

How about that!

 

[77-4speed]

Chris,

Sounds like a good plan. With a splitter and some hoses I could actually set it up so that I could control when the heater core is bypassed and when it isn't!

I just wanted to make sure I was thinking about the correct hose! Hate to do all that work and then realize it was on the wrong part.

Thanks for the ideas. You really are a "custom vette" kinda guy, always thinking outside the box.

-Russ

 

[Bob Chadwick]

Russ,

Vacuum stops the flow of hot water.

I pulled this valve and replaced it with a manual valve rather than cut the line and have a second valve in place.

Bob

 

[77-4speed]

Thanks Bob,

I wanted to make sure I had the right part in mind. I was pretty sure from your description of the part you replaced but now I'm certain. I might try to do some creative engineering to see if I can't put a vacuum switch in the car so that the heater core only receives coolant when the temp is set to hot. We'll see.

Thanks guys.

Russ

 

[Bob Chadwick]

Good luck Russ. I wasn't sure whether or not all the hot water was being cut off by the vacuum switch so I made the decision to pul it. You didn't need a heater core in a C3. You have more than enough heat coming up from the floor boards

Bob

 

[77-4speed]

Bob,

So true! There is enough heat from the exhaust to fry an egg! Have you looked at the rubber lower seal around the shifter? I read in another post that sometimes that thing leaks all the hot air in. I am going to take a look tonight if I get the time. They aren't terribly expensive to replace.

-Russ

 

[Bob Chadwick]

I have an auto so I'm not sure of what I am looking for but will eventually.

I've got the carpet out of mine and am waitingto see what kind of discount 69Crazy can get on the insulating material.

Bob

 

[sac001]

Russ,

Let us know how it works out. I was thinking of doing the same thing on the semi-automatic cut-off switch. Like you said, in the daytime, that heater will cook you right out of the car, especially with the tops off, and driving slow in the sunshine!

Good luck.

Steve

 

[69MyWay]

Here is an idea. Get a EGR solenoid from the junkard. Heck get a hand full of them. There are different types, so the more you get, or experiment, the more you will learn. I would stick with G.M. cars from about 1985-1992.

The older EGR solenoids would simply divert vacuum on or off to the EGR valve based on some input from the computer. The newer ones actually cylce it open and closed at a rapid speed. In any event, you get a solenoid (they are very small and easy to hide). Wire one side to all the time power, then set up a grounding switch. Run the primary vacuum to the solenoid, then to the heater valve. This will actually cycle the vacuum power at a flip of a switch and hold it there until you want to reverse it.

The trick is, some will supply vacuum with no power added, and some require power to close the solenoid and pull vacuum through. I would bet you could easily install a snap switch in the climate control head that would close the ground circuit when you slide the bar to the hot side. Since you would only be connecting a ground, no worries about shorting anything out in there, and no "live" wires to have running through the console. Or, you could just put in a toggle under the dash.

New, these things are like $60 depending on the car, so that is why you want to run the bone yard. Easy to test with a hose, your mouth, and a good 12V battery until you find the right one.

 

[Bob Chadwick]

Thanks Chris. That is a great idea.

Bob