So my '99 recently stopped putting out any heat whatsoever. The thermostat had been acting up, so I changed it as a precaution, and as suspected, I still had no heat.

From there I checked the heater core and blend door actuator. The heater core certainly is functioning properly (and I have the burn on my hand to prove it!) but the blend door actuator was not moving as you moved the temperature control knob back and forth. So I ran to oreillys, bought a new actuator, and spent Saturday replacing it. As luck would have it, I installed the new one in the heat position, which is probably better for winter time.

After getting the dash back together and discovering I had only heat, I pulled out the environmental control panel and checked the temp control knob's rheostat with my multimeter, and the rheostat seems to be providing variable resistance the whole way through.

So at this point I know the heater core, thermostat, blend door actuator, and temp control knob rheostat are all good, and yet the system is not working. With my limited knowledge tinkering I don't even know where to look next. Any ideas would be greatly appreciated!

Did you calibrate the airmix door after you installed the new actuator? I don't know if this will help, but it's worth a try:

It’s time to calibrate the Air Mix Door. To do this, start the car and crank the heat up to max (90º). When the door arm has finished moving
to the right as far as it’s going to go, use the long screwdriver to pop the rod off. Using the screwdriver, try
to push the door arm as far right as you can. Reinstall the rod with the door in this position. Calibration is
done.

Maybe in your case you need to go to max cool & calibrate...

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Resident Tightwad

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Ill try popping the actuator rod off and calibrating it, but the problem is as of now is doesn't seem to be wanting to move at all, in either direction. While I have the dash apart again this weekend, if anyone else has other ideas I should try, I'd love to hear those too.

Anyone think it could be electrical/wiring harness?

Pop the rod off and watch the actuator arm while you run the heat from high to low, low to high, etc. If the arm doesn't move you've probably got electrical issues. If that's the case, I'd start with the connection to the actuator.

_________________

Resident Tightwad

Screw you, Photobucket.