dms0309

My heater is blowing out thru all the vents at the same time, floor, defrost and panel. What do I look for. Thanks for any help.

FOURSPEEDVETTE

Sounds like the deflector door is not closing completely in the heater box under the passenger side dash. The cable probably came disconnected. Drop the carpeted panel under the dash on passenger side. Remove the ECM (electronic control module). It's the first thing you'll see there. Behind it is the heater box and you can inspect the cable connection there.

gerardvg

Hi

The vacuum controls the air delivery, routing the vacuum to the required location like demist to screen, floor and the 4 adjustable grilles to the cabin. You will have vacuum dampers opening and closing what is requied via the selector lever, Check your vacuum supply from the engine and confirm you can see the vacuum dampers open and close things like recirculation damper when a/c max is selected or the demist damper opens to let the airflow up to the windsheild.

The cable is manually adjusted by the temperature lever, the flap will open and close for heater or a/c airflow i believe. I have a shop manual at home i can post a diagram of how it all works when i get home.

Gerard

dms0309

Thanks Gerard, I can check the cable connection to the heater box as FOURSPEEDVETTE recommends but I'm not sure where to check the vacuum supply. any info or diagram would really help.
Dennis

gerardvg

Hi
Here is some stuff to help you from my shop manual.
The vacuum goes from the engine and check valve thru the wiring harness, that will be the easiest to do that the check valve works and the vacuum ball holds a vacuum.
Of course the engine needs to run when checking the heater/ air conditioning controls.

Cliff Harris

Probably a bad vacuum check valve. About $4 at any auto parts store. It's next to the distributor on the driver's side:

dms0309

Is that the valve the connects to the rear of the plenum?

Cliff Harris

Yes.