Update: I HAVE HEAT AGAIN! Turned out to be air in the system. Turns out the guy who did it last time filled the reservoir first before filling the rad from the filler neck, and then topped it off from the filler neck, which probably trapped air into the system. I went ahead and drained the coolant and re-filled it properly, ensuring I bled it well via the thermo bleed valve and the one above the water pump. Thanks for the info guys! This place is awesome.
Yesterday my heat decided to crap out on me (the ONE day that mother nature decides to throw a freak spring snowstorm into my area), I've opened up the passengerside dash to check the actuators, and both seem to work fine, as does the door that opens up when I turn on the AC.
Just to be clear, as I am not 100% sure if they are the actuators I've been reading about that control the heat door, but these two things work fine:
If those AREN'T the actuators/temp door motors, then where is it, exactly?
I noticed it started happening when I was driving last night, the temp gauge was rising at quite a noticeable rate, past the halfway mark (105 Celsius or 221 F) and rising, so I decided to turn on the heat, and thats when I saw the temperature drop rapidly back down to the typical range (~65C or 150F) for my car but the heat would not work.
I also checked under the hood, and when I pinch the tube coming out of the thermostat back to the rad, I can hear the coolant slosh in the tube from the other side of the engine near the belts (the input tube?) even when the car is off. Wouldn't the thermostat be closed when the car is off, and so coolant wouldn't be moving between the two hoses? That is my main clue that I am thinking the thermo might be stuck open.