Heater blend door stuck?

The fsm says, as you gradually turn the knob from max warm to max cool the vlt should increase from 4.5vdc to 0vdc.

 

I tried removing the ribbon cable that connects the switch and testing and got the same results, it seems like the switch is doing nothing at all regardless of if it is connected, set to warm, or set to cool. same voltage all around... I think I'm going to put this back together and pull the original from the truck and swap them temporary and see if I get the same results... maybe I actually have TWO bad switches.

 

I'm sure it's happened before. Two faulty units.

My buddies buddy is having an issue exactly as you're describing in his 3rd gen 4runner. But he's a dumbass and i don't feel like wasting my time trying to help him. Because unlike you, he doesn't seem to want to help him/ help himself.

 

trust me I'm a dumb ass. I don't even need to fix this because it is simple enough to open and close the mixer by hand, but mystery problems bug the shit out of me and I can't stop thinking about what the problem could actually be.

silver lining.. I know a whole hell of a lot more about how the hvac in cars works now... and I'll stick with the cable driven AC systems like in my 92 corolla and my original 96 tacoma over these servo driven controls

 

Ayyyy this should almost be a sticky!!! I had been struggling with this problem on my 98 for almost a month! For me something is binding the cable that goes from the mixer to the heater valve outside, it just won’t budge in any direction so I disconnected it and turn the mixer by hand too but same thing it’s either really hot or cold. Also, anyone know why there could be a breeze in the passenger foot well? At highway speed my passenger can’t last more than 10 minutes without needing like a jacket to cover her feet and I’ve felt it too when she drives, it’s like FREEZING cold but I really can’t see where it comes from

 

welp.

2.72 resistence (not 3) and 2.31v regardless of position of the temp switch. Looks like I got two bad units. Third times a charm, right?

 

Bummer man.

 

This whole actuator problems seems to effect most 1st gens , I’m having a similar problem with my ac (04 tacoma) my servo makes lots of noise when my ac is on , I removed it today and checked resistance according to the fsm it’s checks out , when you add voltage and move the knob to cold it’s doesnt stop and stays, it stops and moves half an inch up then goes back down until it act normal then it does it again , not sure if I should replace

 

yeah I never got mine working. Tried 2 used control panels and 1 used servo and no dice. Tried the relay as well... Tired of throwing money at it and I'm not doing the test procedure properly so I'll just open and close the damn thing by hand

 

Yeah I’ve been dealing with this for a while now , till this morning I decided remove the servo and check the gears for binding and check the resistance , I installed it like 10 minutes ago and no more noises and my ac is at full cold full blast ? Wtf?

 

Try turning the temp knob back and forth about 40 times. Sometimes the potentiometer in the control unit gets dirty.
There will be no voltage at servo motor unless it is being told to move. To measure voltage you have to be turning the knob. As soon as you stop turning it the voltage goes away.

 

I've replaced the ac panel with two others and never got pwr to the servo. tested both the original and a used servo by applying power and they arent burnt out.. just not getting pwr. Not sure what else to try.

 

Subbing, my mixer has issues staying cold. It stays hot no problem, but when I switch to cold, it will go cold for a second and go back to hot. I need to turn it back and forth a bunch for it to stay cold, but there is never a pure blend, its either HOT or COLD. I hear the servo running and sounding like it's struggling too.

 

https://www.youtube.com/watch?v=4i-7GnTXFiY

My truck just makes this servo buzzing noise literally every 5-10 second whether my AC/Heat is off or on. No issues staying cold or hot and everything functions fine. I assumed it was the door actuator being stuck but since everything works that seems unlikely.

 

I have issues getting AC to stick open and I hear this noise when I go back and forth as well.

 

Jon is the potentiometer in the knob itself? If so, will replacing the entire panel potentially fix this?

This is my issue:

Subbing, my mixer has issues staying cold. It stays hot no problem, but when I switch to cold, it will go cold for a second and go back to hot. I need to turn it back and forth a bunch for it to stay cold, but there is never a pure blend, its either HOT or COLD. I hear the servo running and sounding like it's struggling too.

I actually just broke my knob out of frustration so I ordered some aftermarket knobs and a whole panel from a 4runner to get green backlit buttons instead of orange. But if it will fix my *#$*&$@# AC issues too, I'll be happy. Might clean the blend door too.

 

Potentiometer is patt of the main control panel.

 

Cool, so this might actually fix my issue. If not I think I will go and follow this thread for fixing the servo itself.

https://www.tacomaworld.com/threads/air-servo-damper-no-2-possible-aftermarket-part.500522/

*EDIT* I also assume I should be able to access this servo without removing the bezel that surrounds the AC controls I hope? So if I do go replace the AC controls, it should be a set it and forget it, and tackle the servo motor seperately? Or dig into it all at the same time?

 

Servo motor you access from under dash.