Is this a dash heat vacuum operated valve?

[JerryP]

Question what is this, what does it do, and where does the vacuum line come from that goes to it?
Anyone have a picture of how the correct setup looks,

I figure it is the on/off valve for the heater core, not sure if vacuum holds open, or closed, nor where to find the vacuum line that should hook up to it.
I am either replacing the heater core, or hooking up the old one if the old one works.
The line on the valve goes to the rear heater core, and it works very good, heating the entire unit, but it would be better if it all worked.

Also anyone know what that homeless green wire hooks to?

[bluebird]

That home less green wire isn't a wire, it's the line for the valve. I'll bet the heater core has a hole in it. That's probably why it's bypassed. Even if it don't leak it looks like it's full of mud from a mud dauber.

[JerryP]

Thanks, You re right,
I was thinking the core probably had a hole, A new heater core is not expensive.
Now I need a picture to figure out the valve, and hose routing.

[bluebird]

More than likely when they did the bypass, they just looped the hoses. All the valve does is stop the flow so it shouldn't make a difference which on it is installed on. Those hoses should be a little bit different size so you should be able to tell which one goes where.


I would say the valve goes to the rear port on the heater core. The line don't look like it will fit if you put it on the front one.

[HandyDan]

I had the rear heater, too.  As I was driving down the road the rear heater sprung a leak and antifreeze spewed all over the rear of the coach.  It does shampoo up fairly well, though.  Just saying, as old as our units are, keep an eye out for any leak back there.  You don't want to clean up hot antifreeze.  I don't have the vacuum valve like you have.  Mine has a manual cable on the heater valve. 

[Rickf1985]

You might find that the heater hose to the rear also goes to the hot water heater and heats your hot water while driving. My heater hoses Tee off right behind the alternator with the return hose going to the radiator. I can see that hose in your picture. The other hose comes from the engine and goes to the heater valve and then from the heater to ?. I draw a blank at that point. W% For the life of me I cannot remember where it ties in after that. It should Tee into the hose that returns to the radiator but I just do not remember if it does.

[EldoradoBill]

The heater valve in my rig has an inch of green hose coming out of it and I can't seem to locate the rest of it, a diagram shows it originating at the temp lever but doesn't show it full hot or cold. But before I get too worked up on that aspect...I really need the answer to the unanswered question, does the valve default to open or closed? That info will help in my decision on how to proceed...


Bill

[EldoradoBill]

Anyone?

[Rickf1985]

Bill, I am not ignoring you. It is just that different companies valves do different things when the vacuum goes off. Some shut off (most), some go full on (not many) So basically you have to watch it to see what it does. Or disconnect the line while the engine is cold and see if the line ever gets hot when you start the engine.

[EldoradoBill]

Well I located the vacuum switch on the back of the HVAC control and traced it through the cowl to where it apparently burned off atop the manifold. replaced, connected, the valve gets vacuum to shut off the hot water at the full cold setting.


I hope this helps someone else down the road.