No heat from heater 1990 ZR1

[jrd1990zr1]

Thoughts and suggestions please. AC works fine, no codes set, no fuses blown. I only get cold air from heater. Temp gauge never goes above half way. Had heat last fall, but not now. Does this sound like the heater core is air locked? Any thoughts and/or possible fixes are appreciated.

Thanks

[-=Jeff=-]

Have you checked coolant level? When was the T-Stat last changed?

if the car is not getting warm and the temp is showing cool, maybe the t-stat is stuck open

[jrd1990zr1]

Jeff,

Coolant was a little low but not much. Not sure about the T-stat, I have not changed it.

Is it possible the coolant went low and I got an air bubble in the heater core?

Thanks, John

[-=Jeff=-]

possible, but I have a feeling it is either stuck T-Stat or maybe a clogged heater core

[QB93Z]

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

[jrd1990zr1]

Jim,

I see no movement of a door through the heater resistor hole. Top line to heater core is about the same as the metal crossover, however the return(lower) metal line from the heater core is significantly cooler.

I don't see anything in the 1990 FSM about getting to the door, door actuator or motor. Have you done this on your car? Am I missing something in the FSM?

Thanks again, John

[QB93Z]

Originally Posted by jrd1990zr1

Jim,

I see no movement of a door through the heater resistor hole. Top line to heater core is about the same as the metal crossover, however the return(lower) metal line from the heater core is significantly cooler.

I don't see anything in the 1990 FSM about getting to the door, door actuator or motor. Have you done this on your car? Am I missing something in the FSM?

Thanks again, John

No Movement of the Blend Door is a good indicator of a problem. I did a repair (replace) to my Blend Door Motor on a 1994 ZR-1 which does not have a glove box and the blend door motor is on the bottom of the AC Duct.

The operation and diagnosis of the HVAC controls is (in the 1994 FSM) described in bits and pieces in Volume 1 and in Volume 2 and it takes a fair amount of research to figure it all out.

Here is the Thread where I fixed my problem which may be similar to yours>

http://www.zr1.net/forum/showthread.php?t=27542

Jim

[-=Jeff=-]

If I recall, the blend door motor might be Accessible by removing the glove box and glove box door. I know I can see the manual assembly from there.

I forgot about the Electronic blend door.. I have Manual AC which on my 90 I prefer

[BigJohn]

Glove box???

[-=Jeff=-]

A glove compartment or glovebox or glovie is a compartment built into the dashboard, located over the front-seat passenger's footwell in an automobile, often used for miscellaneous storage. The name derives from the original purpose of the compartment, to store gloves. They were sometimes in a box on the floorboard near the driver, hence the alternate moniker of a "glovebox". In most vehicles, the glove compartment closes with a latch, with the option of being locked with a key (often desirable when using valet service, or when parking while the convertible top is down, or when the compartment contains a mechanism to open the trunk).





Yes those of us with 90-93 cars had that privilege of a glove box..