Bobbyg75

Researching heater hose replacement and I find in several parts books my 75 A/C auto is supposed to have a "hot water valve" in the 5/8" hose between the intake and the heater core. Not on the one I am restoring! Is this something that was removed by previous owner and if so, what is it and where is it located?

Thanks in advance,
Bob

80TexasC3

Bob,

On my 80 (not sure if it's the same on yours) the valve is located on the right hand wheel well (bolted to it). Is basically a simple vacume controlled valve that is triggered by a switch behind my glove box. When the temp lever is all the way to "cold" is triggers the switch and closes the valve thus keeping hot water from entering the core. Thus makes for a more effective vent/AC. Sounds like a previous owner ran a solid heater line from the intake manifold to the heater core.

Hope this helps...

Ed

Jack71

The water shutoff valves were located on the passenger side fender. They are vacuum operated to stop the flow of water when you turn on the AC.

mooneyd

Does it operate when the temp. lever is set on cold or when the AC is actually turned on? I was going to put a manual valve in there so I could stop the hot water even when the AC is off. But if its controled by the temp. lever then I would just leave it on cold. Need to cut back on hot air coming in the lower vents on the drivers side!

NHvette

If you mean the kickpanel vents - then the valve will not effect this. If
you mean the floor heater outlet - then yes.

Mine (no AC) came with a stainless ball valve inline for manual
heater core shutoff. Some suggest a valve in each hose - to
prevent convection heating to the core.

Ball valves available at Home Depot, etc.

I can't say for sure, but I though the vacuum controlled valve was
controlled by "AC on", although it makes more sense to
regulate it by temp.

Paul Borowski

I have a late '75 A/C auto coupe(July 12, '75)and it NEVER had one of these. I do not believe a stock '75 had one either like some people claim. I do not think these came out until '76.

Bobchad

According to what I have read, the vacuum valve is only supposed to work when the a/c is on but I couldn't find any reason why it wouldn't work anytime the temp control is all the way to cold. There is a vacuum switch that is activated when the slider is slid all the way to the left. As I recall it was on top of the heater box and in order for it to function properly the spring loaded wired from the controls to the top of the heater box needs to be adjusted properly.

80TexasC3

There is a switch behind the glove box that is triggered when the cold/hot lever is all the way to cold. Being on AC vs Heat on the top lever does not matter.

One point I found on mine... the switch was not activating due to the trigger arm not being long enough to engage it. I simply built up the switch about 1/4 of an inch and that did the trick. Now works great and AC is much more effective while vent is actually the temp of the outside air without any hot water bleed.

75Rag

My stock 75 non a/c has one, but I have also added a manual ball valve to further restrict the flow ......

It works.

Steve's74

I see no sign of my '74 with factory air ever having one either. Does anyone have a '74 with a water control valve?

Steve

markdtn

Dr Rebuilds catalog says only 77-82 have a water shutoff valve, but the diagrams show late 75-76 and 77-82 have them. I thought it was late 71 up that had them, but I guess I was wrong. In any case, they are a nice thing to have to stop the hot water flow and help interior heating issues.

Pete76Shark

My 76 has a vacuum shutoff valve (stock) and it is located just a few inchs from where the heater hoses join up to the heater core, under the car. It think this is the stock location.

The vac line that goes to it works off of the temp part of the climate control. As soon as I move the temp slider past the coldest point the vac line opens the shutoff valve and I get hot water to the heater core.
The other climate control thing (max a/C, vent, heater, defrost) can be in any position and it has no effect on the vacuum to the shutoff valve.

Some owners have installed ball type shutoff valves in both heater hose lines to ensure no hot water gets to the heater core. I have this on my list of things to do.

Right now I have the heater hoses joined together and the heater core is brand new and bone dry. I did this to help me resolve a hot vent air problem. Which I have resolved so maybe this coming winter I will re-install the heater hoses to the core.

IF you are thinking of going the ball shutoff valve then do a search cause at least one other forum member has done this and posted detailed instructions....the 2 heater hoses are not the same diameter..at least on my 76 that's the case.
Good luck