HVAC from face to feet to defrose

[Crafter]

Here is an interesting one I can't figure out.b

My AC won't switch from defrost to face.. or face to feet.

This is what I did. I'll do my best to explain. I remember while changing out the blower motor I realized every time I disconnect the power lines to the actuators that move the flaps for face or feet and reconnect the power.. the motors on the actuators reset themselves to find position.

Now I took the wire that controls the face actuator and connected it to the feet actuator to make sure it's not the actuator. So the actuator works fine and the flap works fine, it's just I have no power signal going to one set of my wires. Could it be a fuse or am I missing something?

Could it be my controller unit is messed up? I appreciate all the advice. Thank you!

[Waterloo]

Well, I just went through this and it was the HVAC control head unit with the knobs, I had to replace. ALSO! There are two TSB's relating to TWO potential FIRE hazards related to your issues. Keep reading and make these repairs immediately.

To test this the HVAC control unit, I used a regular 12 volt test light grounded to the cab. Pull the connections off of your actuators. Turn the key on, to start position, no need to start the truck, but you can if you want.

One at a time hold the tester probe to one of the metal pins in the connector from the HVAC control and turn the HVAC control knob that controls the actuators, the face to feet knob. You will test each pin, as one is power and one is ground. The HVAC head unit only sends an electrical signal to the actuator when the knob is turned. Do the same with the hot to cold knob as that controls your other actuator. If there is no signal being sent from the HVAC unit, you know you have a bad unit and should replace, and they are not cheap. So test this multiple times to make sure you have a good ground on the 12 volt test light, etc. Keep reading...

THIS IS VERY IMPORTANT! DO THIS! As you are having these issues, you may have another problem that is very common to these Prostars and there is a TSB with this part needed to fix, 3865234C92. I would just order this part right now and install asap. There is a real issue here that could cause a FIRE. Get this harness.

Pull the connector apart that goes to your blower motor and linear power module from the harness. Check for melted connections. If there are melted connections you will see it. This is common on these ProStars and may also be the reason that your HVAC control unit is not working, or fried.

If it is melted, clean up the connection as best as possible. I used a small pick and screw driver to pick the melted plastic out and realign the pins. I then installed the part the TSB called for, again, here is the part number, 3865234C92. The part is a harness or pigtail. It is a foot long with the correct connection to go in between your HVAC harness and blower motor/linear power module harness. It has a soldered in resistor to dissipate the heat that the blower motor generates, and they generate quite a bit, enough to melt the connections and possibly cause a FIRE. As your truck and wiring age, this potential risk for fire will go up. Get this part.

There is also a TSB on the Linear Power Modules, those too were overheating and could cause a possible fire. You may want to pick up one of those too if you have not replaced in awhile. If you have never replaced the linear power module, ask the dealer to run your vin to see if you have one of the bad units. This relates to the new harness with the resistor. Both are fire hazards. If you have one of the old ones, the dealer may replace for free under the old and now expired TSB. If not, keep reading, I found a cheaper solution in regards to the $250 LPM from the dealer.

The TSB harness was $45 at my local dealer but can be had cheaper on the internet. I would get this part at the dealer, that way you know you are getting the correct part. The linear power module is around $250 at the dealer, but can be had cheaper on the internet too. I found one of the updated ones here for $44 and installed in my truck. http://www.truckerac.com/blower-resistor...21021.html I bought one of the dealer $250 ones and compared to the $44 one, they are identical right down to the stampings, barcode and manufacturer. Get the $44 one.

I hope this helps, as my wiring was overheating and routinely taking out the blower motor, and I believe this took out my HVAC control unit too. There is little if any info on these issues. My dealer did not even know about this until I made them look and dig deeper into their TSBs. We found the TSBs not under HVAC, but under wiring, imagine that?

Oh, my truck was not on the TSB bulletin either, but I sure had the fire hazard problem. So even if the dealer says you are not affected, I would not trust them, do this repair.