The temp slide ron my HVAC controls stopped working. It doesn't do anything at all...What does it exactly do? I know there is a cable that moves the door under the dash to either block off the air going to the heater core,or open to aloww heated air through, but it also has vacuum lines that are switched when it is put to full cold. Maybe it is those, but what do they do?

 

Any ideas?

 

Slider controls only the door movement as far as I know. The vacuum lines change 1) which vents are used, and 2) the heater bypass under the hood.

 

I figured that was what the vacuum lines on the temp slider are for. I know the door moves because i moved it both by hand and watched it move...but no hot air comes out of the vents. I know that the engine temp was high enough for it to work...I'll have to see on a bit cooler day.

 

That could suggest the heater control valve might be stuck diverting coolant from the heater core, a vacuum leak to the diverter (constant vacuum) or, the heater core is blocked with crap (dirt from old, crappy coolant/poor maintenance) and hot coolant isn't circulating through it (like my s10).

 

I believe I know what it is...I took the little vacuum valve from the temp slider out of a junkyard and replaced mine to see if it was any better, and I do believe it's leaking, so that must be it. I'm taking my whole dash out today to look at the whole system and make sure there are no leaks and everything is hooked up right. I'll fix it then.