I have problems with my whole system. But since its getting cold I need my heater. When I switch to heat my air does not get cold. It blows fine but I can not hear my heat door open so the air can flow through thr heater core. I have an 86 Elky. Is the heater door controlled by vaccum or wire pull. Any suggestions or advise ti fix this? Thanks

If it's blowing out the floor when you choose the heat mode, then I would check the temperature blend door. It's the one controled by the sliding lever and is cable operated. Remove the glove box and look on top of the heater a/c box.

When you choose the heat mode with the top lever or when you move the bottom lever to hotter?? which one is cable operated or are they both?

the temperature lever is cable operated.

The cable on mine is connected and the door opens and closes. But still no warm air? What now? any ideas?

Low coolant, air in the system, restricted heater hose, retricted heater control valve or restricted heater core.

Heater systems (http://elcaminocentral.com/modules.php?name=NukeWrap&page=articles/heat/hsystems.html&height=3000&width=100%)

Thank you. Very good info i am now armed and dangerous with that much info!

Thank you as well, I will check both. Form that info I have a feeling I have a clogged heater valve and the coolant isnt getting to the heater core.

It was the heater control Valve. The original valve is steel and was corroded and stuck closed. Heater system works great now!! Thanks for all your help. 8)

Thanks for posting what your problem turned out to be. A lot of these posts read like good mystery novels, except we never get to know how they turned out!