The heater controls on my truck, a '88 F150, 300 cid, no A/C, doesn't seem to have any effect on the temperature of the air coming from the vents. The fan speed and vent location levers seem to work fine, but the hot cold selector must not be working properly. The lever has a slightly more resistance than I would expect and makes a clicking/snapping sound when pushed all the way to either side. I'm guessing "mixing" valve must be stuck open or partially open, where is this valve located?

Driving with the heat on isn't much fun with the 95° weather we've been having lately.

Thanks
Kevin

 

I cannot remember for sure if that switching valve is under the dash or out in the air box under the hood for that year. See if you can locate where that cable goes and follow it. Normally it will be broken at the door. And you can manually move it into place until you get a new one, but at least it will cool down for ya,.