On the hot water valve in the heater hose of a 78 L48 with AC, does the vacuum turn the flow of water off or is it off until vacuum is applied?
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Re: Hot water valve
Doug------
I believe that it's a "normally open" valve and closes when vacuum is applied. However, I'm not 100% sure.In Appreciation of John Hinckley -
Yes!
Joe's guess is dead nuts on. The valve is normally open.
Rationale: should the system fail, do you want 'em to sweat a bit in the summer or risk life/limb/property by not having heater/defroster operable in the winter? The answer is obvious...
That means every time you shut the engine down and vac bleeds out of the system, the heater shut-off valve opens allowing the heater core to heat soak via thermal convection. In hot summer weather, some complain of hot air coming out of the heater box after short stop(s) (gas, lunch, Etc.). So, you learn to start the car and run the A/C on MAX long enough to pump heat out of the heater core...Comment
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Re: Yes!
Thanks! Now I understand why it's so hot inside the car. My AC is blowing on the floor only, but the headlights still open fine so I must have a vacuum problem in the dash somewhere.Comment
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Re: Yes!
Hi Jack:
Apparently GM changed the way the valve operates for the C3. In my 1967 C60 car, the valve is normally closed and requires vacuum to open.Comment
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Re: Yes!
So if there's a malfunction, and it's 20 below - no heat.
Who said they didn't design these cars with collectors in mind 50 years downstream! This was clearly a "design decision" as they knew collectors wouldn't be driving their C2 Corvettes in such cold weather and the lack of coolant going through the core in summer would keep the car cooler, even when the A/C doesn't work.
DukeComment
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