Hey there. I have a few problems with my 91 NA, but right now I am just curious as to what can cause a heater to work intermittantly? I am pretty certain that the heat-slider on the dash is working properly, I can hear it move while I slide it. What else could be causing my heater to be blowing not-hot air even when my engine is running, and warm. Leaks? bad boses? jsut wanna know what can casue a heater to fail..

Thanks,
Andrew

 

Last one I found doing what you describe had a loose screw inside the Logicon from the display panel.

But if you have the air/mix motor moving everytime then its more than likely the heater core itself.

 

By "the heater core itself", you mean it might be clogged or have a hole in it that is letting air in? Anything other than? I dont notice any coolant under the car when it is warm or cold....

Will disconnecting the heater hose that leads into the firewall + the heater core tell me anything? I've heard that heater problems can be caused by that hose, but it looks OK in my car.