Heater Control Valve ?

[71383bee]

I've traced down my lack of heat issue to the heater control valve.  It appears to be a replacement Everco H1948 series that has the heat control cable.  I tried gently moving the lever on the valve and its frozen.  Tried soaking it in pb blaster now, but i'm not hopeful it will budge.  I'm not sure if the cable itself is bad too, but in my opinion the valve should move more easily with me pushing on it. 

I have two questions:

1.  What does this valve do?  it looks like it opens a valve to let coolant through the heater core.  Why though does it need a diaphram and what control cable is it attached too?  This is an A/C car BTW. 
2.  What was used by the factory?  Is this a factory part?

The reason I ask is I have searched for heater control valve replacements and they are all over the map.  some cable operated, others vacuum, and vary in complexity. 

Car is 73 Challenger Rallye 340 4 speed w/ A/C - SBD 319

[Skid Row]

It's my understanding that A/C cars were vacuum operated, and non a/c ones cable operated.

[Headjam]

Sorry @71383bee, I only know 1970 AC E-bodies. Here are a couple of photos of the (rather unreliable) 1970 water control valve. This valve is mounted on the passenger side inner fender and is cable operated. The non-AC cars do not have an external valve like this. Not sure what they did in 1973 but you can find out by looking at a parts catalog or service manual (posted on this great website!). 

[Squire Edgar]

My 1973 factory a.c. Rallye 318 is cable operated

[1 Wild R/T]

My 1973 factory a.c. Rallye 318 is cable operated

As it should be....

[1 Wild R/T]

Your valve should look similar to the one below....   

Non A/C E bodies didn't use a valve, A/C E bodies use a cable operated valve... 71-74 use the valve below... 70 used the valve posted above but they are interchangeable with the cheaper more reliable 71-74 valve...

[Rich G.]

The valve shuts off hot water to the heater core so the a/c is more efficient. Vac. or cable does the same thing. My 71 and 73 were both cable operated. Pretty sure all e bodies were.

[71383bee]

Thanks guys.  I just got my 73 FSM last night and it shows the same water heater control shown by headejm. 

Its definitely cable operated and a numbers matching A/C car. 

What makes the stock valve so unreliable?  From a personal note i like the more simple mechanical version you posted 1Wild.  Seems very straightforward and less prone for something to not work.  Why do the others need a diaphragm?  is it a pressure issue like water hammer?  I've never had a stock A/C car before and im starting to appreciate the ingenuity.  There seems to be alot that goes into it!

[1 Wild R/T]

I can guarantee you your service manual is using a picture carried over from 70.....  The valve I posted is correct for your car....

The 70 valve is plastic, they crack/warp causing a coolant leak....  My R/T looks pretty stock & because of that I've searched for & paid the price for the original style valves... I've had to replace it about every 3-4 years for leakage.... This time I finally said enough & bought a 71-4 style valve..... 

[71383bee]

Cool!  thanks for the advice.  I'd prefer their simplicity and order one up.  Which is more "correct"  i see the gold cadmium style ones and the silver style? 

[1 Wild R/T]

Silver..

[screamindriver]

What makes the stock valve so unreliable?

Two things generally happen to them...First, the bakelite body tends to warp/crack when it's exposed to heat over a period of time...Secondly, the rubber diaphragm degrades leading to water leaking out the tower of the unit... NOS units are getting older and some I've used won't make it past a few years...