Want to add heater control valve to '90

[Agent13]

Hello everyone,

I am interested in adding a heater control valve to my '90 C4. I was wondering where I could connect the vacuum line from the valve to since the '90 didn't have a factory heater valve.

Any input would be appreciated.

[vetteoz]

I just installed a manual valve on one of the heater hoses ;
turn it off in summer to keep heat out of the heater core and turn back on for winter

[HardcoreABN]

my question would be why

[vetteoz]

Originally Posted by HardcoreABN

my question would be why

As I note above ; the late cars have full flow of hot coolant inside the car at all times so you can get heat " leakage"
out of the heater core when you have A/c on.
Early cars shut off the flow completely when heat was not in use

[HardcoreABN]

Originally Posted by vetteoz

As I note above ; the late cars have full flow of hot coolant inside the car at all times so you can get heat " leakage"
out of the heater core when you have A/c on.
Early cars shut off the flow completely when heat was not in use

very aware of this. This is really just a band aid for other HVAC components that need to be replaced.

[vetteoz]

Originally Posted by HardcoreABN

This is really just a band aid for other HVAC components that need to be replaced.

The foam rubber seals on the blend door disintegrate and the door no longer seals tight allowing heat out

[wildcatlock]

Originally Posted by vetteoz

The foam rubber seals on the blend door disintegrate and the door no longer seals tight allowing heat out

But if an automatic valve was wanted couldnt it be tied in to the vac line to the blend door? IIRC blend door fails to cold side thus heat would be applied vac as would the flow control valve.

[vetteoz]

Originally Posted by wildcatlock

But if an automatic valve was wanted couldnt it be tied in to the vac line to the blend door? .

Blend door position is by a electronic stepper motor controlled from the HVAC head unit
Vac only controls vent positions