96 Tahoe Heater Only Blows Warm Air

[Novasmihjohn]

FYI, I decided to unplug the heater control valve vacuum tube that goes to the solenoid and my heater immediately started blowing hot air. Previously I had only tried unplugging the vacuum line from the engine to the Solenoid and it made no difference.

I tested the voltage going to the solenoid and it was 12V when the cold air is on and 0V when the hot air is selected. I assume that’s working properly so I must have a bad solenoid.

Will update after I replace with new.

Where is your vacum attached to the engine. I have the hose and elbow but can’t find where it’s attached to draw vacuum

 

[SUBURBAN5]

Where is your vacum attached to the engine. I have the hose and elbow but can’t find where it’s attached to draw vacuum

If a vortec 5.7, look next to pvc valve and throttle body. Should be a small plastic hose that connects to the nipple under the pcv rubber elbow, and goes across the manifold and back to the fire wall solenoid, that has 2 ports

 

[Laredo1307]

I believe some vehicles like the single cab trucks don’t have the vacuum actuator but it connects to a PVC on the driver side of the engine and has a hard vacuum line that runs over the top, behind the throttle body.