[spike753]

Not sure if this fit better in Heating and Cooling or electrical...

My HVAC control is on the fritz I believe.

The middle knob is the problem I think it has worn out. It will not turn on the blower fan at all levels. If I push/pull/wiggle the knob just right it will go other wise I get either all or nothing. It will be dead through the whole range of fan speed levels unless on its on the highest speed setting on the a/c side which also does work still to get the blower going

In the picture this is how I had to set it the other day in order to get heat blowing. The actual heat and ac work fine when I get the fan turned on.

As I said I played with it yesterday and was able to wiggle that knob and get the other fan speeds to engage.

I am sure the problem lies within the switch. I have yet to pull it to see if there is some mechanical part to the switch that can be R&R'd or if it just an circuit board that is cutting out and should just replace the whole switch.

I plan to pull it later today, don't think it will be a terrible job or trouble finding the issue but I figured I would post it up here see if anyone else had run into that before.

EDIT: I did make sure the knob was seated on the control unit correctly and matches up right with the unit. I know someone will ask that

 

[KenBerry]

I had a similar issue with the temp control. The knob has a small inner plastic piece that fits on the stem and that cracked so it felt like it was properly seated but it was actually able to rotate without turning the stem. Before tearing into the dash I'd take a minute to pull the knob and take a close look for cracks.

 

[spike753]

Ya I had pulled it off and it and took a peak at it. It still does turn the stem. You hear the "click" as it goes into each position.

 

[spike753]

Just to follow up here in case any one else has the same problem, replacing the hvac switch box DID fix the problem right up.

 

[Lazarus Truck]

If it controls the fan-speed at High-or nothing, then it is usually the blower resistor. Standard Motor Products (the only quality manufacturer that I still believe in for electrical parts) Pn# RU109. Here's the Amazon link for it. About half the price of the local store if they can even get it. Never buy "Dura-Crap" electrical parts!
http://www.amazon.com/Standard-Motor-Products-RU109-Resistor/dp/B000C7ZUF6

 

[spike753]

Thanks i will keep that in mind if it starts acting up again. I had just went to a salvage yard and pulled a oem hvac switch from there and it works great again at all speeds. Before you would have to wiggle it or pull/push alittle on that middle knob to get the intermediate blower speeds to engage. The whole white side did nothing at all. But after swapping in and hooking up new module every thing works great again. I think just after 180 thousand miles it was wore out.