‘70 Belvedere AC/heat questions

[Sonny]

I am rebuilding my dual ac/heat heater box and ordered a new core ($250 from year one, ugh).
Question: can I hook up only the heat for now by bypassing the water valve assembly? I’ll work on the ac this spring. What does the water valve actually do? How does it work? I have the push button vacuum controls.
Thanks.

 

[JimKueneman]

I am rebuilding my dual ac/heat heater box and ordered a new core ($250 from year one, ugh).
Question: can I hook up only the heat for now by bypassing the water valve assembly? I’ll work on the ac this spring. What does the water valve actually do? How does it work? I have the push button vacuum controls.
Thanks.

Where is the valve? Is it one in the fire wall or is it in the heater box next to the heater core?

Jim

 

[Sonny]

Where is the valve? Is it one in the fire wall or is it in the heater box next to the heater core?

Jim

This valve on the firewall.

 

[JimKueneman]

Well on a '68 that is connected to the temperature cable and it modulates the coolant that gets to the heater core based on the temperature setting on the dash. The '68 originally had a feedback sensor from the interior that force it into the a "more hot" mode until the interior heated. It look like in '70 they may have changed that feed back to some thermal vacuum sensor that puts vacuum to override the dash setting based on a sensor in the coolant?

Jim

 

[Sonny]

Well on a '68 that is connected to the temperature cable and it modulates the coolant that gets to the heater core based on the temperature setting on the dash. The '68 originally had a feedback sensor from the interior that force it into the a "more hot" mode until the interior heated. It look like in '70 they may have changed that feed back to some thermal vacuum sensor that puts vacuum to override the dash setting based on a sensor in the coolant?

Jim

Thanks Jim. The heater core I ordered has 3 copper lines that connect to another valve shaped like an “h” inside the box. Can I just use 5/8 hose and a T to replace the h valve Inside the box? Just want heat for now.
Sonny

 

[JimKueneman]

Thanks Jim. The heater core I ordered has 3 copper lines that connect to another valve shaped like an “h” inside the box. Can I just use 5/8 hose and a T to replace the h valve Inside the box? Just want heat for now.
Sonny

Yes the "h" valve is so when you have the AC on the heater core only gets fed with 1/2 of the core. If it was the entire core it would completely over power the AC evaporator and you could not blend the AC with a bit warm air. A fully fed heater core would completely over power the evaporator and you would get full AC or full heat, nothing in-between.

 

[Sonny]

Yes the "h" valve is so when you have the AC on the heater core only gets fed with 1/2 of the core. If it was the entire core it would completely over power the AC evaporator and you could not blend the AC with a bit warm air. A fully fed heater core would completely over power the evaporator and you would get full AC or full heat, nothing in-between.

Got it. So if I use the 5/8 hose and a T to make the h shaped connection I’ll just have full heat and the other valve on the firewall controls temp if I hear you correctly.

 

[JimKueneman]

Got it. So if I use the 5/8 hose and a T to make the h shaped connection I’ll just have full heat and the other valve on the firewall controls temp if I hear you correctly.

Correct.