ZR-1 Net Registry Forums - View Single Post

QB93Z · 08-30-2017

You can check the coolant flow to and from the heater core with a thermometer on the pipes in the right side of the engine bay.

The problem could also be a stuck Heater Blend Door. The Heater Blend Door is located between the heater core and the AC Evaporator in the AC Ventilation assembly. It is above the passenger side, lower dash panel.

You can see the Heater Blend Door by removing the AC Blower Control Module from the Ventilation duct in the engine bay, near the firewall, inboard of the coolant expansion tank.

With an assistant you can observe the operation of the Heater Blend Door by removing the AC Blower Control Module and looking in the hole with a flashlight. Turn the Ignition ON. Have your assistant change the AC/Heater thermostat on the dash from 60 degrees to 80 degrees then back to 60 degrees. The door should move. The engine does not need to be running to do this check.

Good luck,

Jim

08-30-2017	#5
QB93Z Join Date: May 2007 Location: Westminster, Maryland Posts: 3,684	Re: No heat from heater 1990 ZR1 You can check the coolant flow to and from the heater core with a thermometer on the pipes in the right side of the engine bay. The problem could also be a stuck Heater Blend Door. The Heater Blend Door is located between the heater core and the AC Evaporator in the AC Ventilation assembly. It is above the passenger side, lower dash panel. You can see the Heater Blend Door by removing the AC Blower Control Module from the Ventilation duct in the engine bay, near the firewall, inboard of the coolant expansion tank. With an assistant you can observe the operation of the Heater Blend Door by removing the AC Blower Control Module and looking in the hole with a flashlight. Turn the Ignition ON. Have your assistant change the AC/Heater thermostat on the dash from 60 degrees to 80 degrees then back to 60 degrees. The door should move. The engine does not need to be running to do this check. Good luck, Jim Last edited by QB93Z; 08-30-2017 at 07:17 AM.