UPDATE: FIXED! - need some help w HVAC servos, I screwed up

UPDATE: fixed, had to re-clock the gears and everything works as it should


I ran wiring behind the dash to the center console for switched lighting. Unknowing to me, the wiring was interfering with the driver side plastic gears for the HVAC. I was getting a plastic sounding pop/click on startup and shutdown. (HVAC moving positions from what I'm told)

I discovered/fixed the wiring issue this weekend, but the gears are no longer moving and I only have defrost air, regardless of position selected. I do have independent hot and cold air, so I don't think it's the blend door.

Are the plastic gears suppose to move on startup?

Any way to jump-start the gears moving again? I don't know if they are locked up or the servo motors are fried.

Are there seperate fuses for this area I can check?

I am trying to trouble shoot before buying a servo assembly and removing the dash panels again.

Thoughts?

 

I did the same thing. Do a search on “blend doors” and you’ll find that the gears have a specific alignment, which is pretty hard to do without taking the whole dash out.

 

I've done it, too. Yes, the servos go through a startup process with key to ignition. If they're bound on their bootup, they'll be disabled from operating.

You can actually remove all of the servos without removing the dash. I think I had to overdrill a hole to make screwdriver access to one of them. While a PITA, it's not as bad as removing the dash/steering column entirely. Do that and validate they're all fine. Then watch some YouTube videos on timing and expect it to take a dozen attempts with rubber bands before everything magically pops back in.

 

Is it any easier to replace the entire servo until as opposed to each motor?

 

You're still assuming that your servos are bad without testing them. I also thought mine were shot until I pulled them off and cycled them. Again, I think it's a just a programming feature which prohibits them from operating if bound.

It's been two years since I've been in there, so I'd wait to hear from someone else, but I don't believe you can replace that sub-assy without removing the blend box.

 

If they are bound on bootup, how am I fixing that? So yours were not broken, but bound up and by removing, manually cycling, and replacing, they worked?

Nothing is moving on startup. If they were broken, I assume the gears would be moving but nothing actually changing.

If I remove and replace, will the servo assembly only "click" back together a certain way?

I dont understand how the system works, which is what I am asking. Is there a way to re-set the servo without pulling them? fuses? re-boot?

 

Servos are not digital so there's nothing to reset electronically. The blend doors are made up of gears that have grooves where things have to be aligned (hard to explain) but the wires likely popped them out (of the grooves) or it's just broken. Hard to align things when it's hard to see. Some people get lucky.

 

Exactly. The servos are splined and slide off of the gears. It's likely that your gears became mistimed with the wire and now prevent the initialization sequence, so the HVAC ECU has shutdown servo operation. Remove them so the motor controller can do its thing.

No. That's why I said it takes a dozen attempts. It's possible to reassemble and have it mistimed. This is when you'll see guys complain that their blend door is stuck in one or two positions.

I can't really explain this more. It's only a few bolts to remove the single kick panel and you're looking at all of this. Have you watched the YouTube videos yet? You're dealing with a mechanical assembly which isn't set correctly. There isn't an electrical solution here to get around that.

 

Pulled the lower panel, drilled the hole, removed the servo assembly. Are these gears suppose to move freely?





I messed with the gears/blend door in center of dash, that all seems to be moving freely and working correctly. I put the truck in ACC and air moved through the center vents and the flaps seemed to work when I manually moved the gears on the box.

 

but they would still be moving on startup, which they are not

 

so how does this process get re-set? If I just pull it off and put it back on its going to be the same result. Also, my digital hvac selector panel takes about 15sec to come on after startup, which i assume is related to this whole process.

 

One of the YouTube videos I have seen is the plastic axle that each gear has can break and you don’t know until you remove each gear from the housing the gears will still turn freely if the axle is broken

 

https://www.youtube.com/watch?v=wVhRP89FYpg

I watched the video again. I took apart the servo motors, nothing is broken. Around 11 min he plugs in the harness to the servo and the gears turn. Mine do not. Along with the digital faceplate being blank for 15 sec on start-up, I'm convinced my HVAC is in "limp mode" and needs to be re-boot.

Im pretty sure this entire removal was completely nu-necessary. Can an OBDII code reader clear HVAC codes and re-set this system?

 

It’s worth a shot I have never heard of the HVAC going into limp mode though

 

If yours isn't, then yeah, I think you're right. Have you checked the plugs on the HVAC panel? All of the HVAC controls get sent over CAN on 2.5s (2.0s have a mix of LIN/CAN). I'm uncertain on OBD2's capabilities for a reset.

 

Checked all of the fuses? Tested the servo motors out of the truck individually?

 

Both servos are in fact working. I heard a noise after shutdown and looked under to see the top servo turning the gears. I marked the lower one and that witness mark has moved, so both are working.

When I had it off, the gears opened and closed the doors correctly. It's like the HVAC panel has shut down.

 

UPDATE: FIXED! I watched the youtube videos again and noticed the starting positing of my gears was different than the video. I dis-assembled the servo motors and clocked the gears to match the video. Got the arms in the correct positions and installed the servo assembly. Everything works as it should. So nice to have A/C again, and I would not have been able to sell the truck without getting this fixed.

 

@ThatGuyTheCooler- It seems I am in the exact same situation as you. I replaced my servo motor thinking that would solve the issue but no gears are turning and I also think the entire replacement was unnecessary as the old servo motor seems fine. I have taken the new servo motor in and out several times and the gears still don't seem to be turning. I installed my servo motor to the below video which was very helpful to get everything aligned.

https://www.youtube.com/watch?v=Yo9HTgMO2tU

It seems that the gears turn for people even before they set the servo motor back into place, much like you noted. Mine do not. You noted that your servo motors started turning before you got the final fix. Any insight into what you did do kickstart the gears moving? It seems I am stuck at the same place you are.

Do you think I need to open the servo motors up and move the gears as you have noted in the image? If I do this can I still install it back in the truck using the same method as previously noted in the video above?

Any help would be greatly appreciated as it sucks being in winter with the AC on and defrost not working.

 

I put a white witness mark across the gear/case and after a minute or two after the truck turned off, the gears will turn, attempting to reset.

In my case, once the gears and assembly was properly aligned, everything worked as it should. In order to easily align everything, use one of the diagrams online, the servo cases come apart and you can assemble it on the truck. Once it's all aligned the servo motors can be reassembled and plugged it

 

You put this white mark right after you installed before starting the vehicle then turned the truck off and it moved slightly after that?

For alignment there are two aspects to this- the servo motor and the levers and gear on the truck.

- For the levers and gears on the truck I assume you put them in the positions that are recommended per the image below.

- For the servo motor are you saying correct alignment is per the below image?


If the above two are correct, I think I have installed it correctly as it fits in very snug with no play yet no gears are moving.

 

Leave the servo cover off and plug in the motors, after you turn the truck off, give it a few minutes and you will see the motors activate (resetting the position)

I set the gears to the recommended start positions, but did not need to use the dental floss/rubber bands. I then put on the servo cover (motors removed). I had the motors disassembled and placed the gears on in the correct positions and assembled the motors on top of the cover. It will work if all the gears are in the correct positions at start. You can buy the entire servo assembly in correct positions, or just the motors if one is blown

 

Unfortunately I could not get this to work.

As mentioned, I have a new servo motor that I installed and tried to turn the truck on and off and no motors are moving. On startup it does sound like some gears are trying to move, maybe HVAC maybe stereo, but nothing visible is moving anywhere on the servo.

I also took the original servo motor, disassembled the motors put the servo cover on in the correct positions and reassembled the motors and turned the truck on and off. Again no movement with the motors.

I have no idea why this is not working. What am I missing? Any other insights or thoughts?

 

I would hook up a voltage tester to the wiring going to the servo harness and verify its not getting power at any point in the operation (startup, running, after shutdown...)

 

Well I was hoping this was my problem, but I pulled all the plastic today and got my head under there and it seems to be working properly. As far as I could tell standing on my head anyway. I put a black mark on the white bit you can see from the outside and went through each position and it indexed to a different spot with each change. It was a little noisy, but nothing concerning and nothing that appeared to be binding. The lower one for heat/ac seemed to function properly as well.
Seems like my issue might be with the blend box. With AC I have little to no cold air on the driver, good bit on the passenger. Face vents don't seem to put out much air, either heat or AC, but foot and defrost are fine for volume on both sides. I also have absolutely zero heat no matter how long I let it run, stays ice cold in winter. All that made think it was these servos but it seems not.

 

Yep, went to put driver servo assembly back in today and this fell out. Time to find a box