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My 2012 VW Passat has dual AC zones. The passenger side AC is not blowing cold air. The Driver's side does. in my slow debugging routine, I am looking at the Wiring Diagram, but I cannot figure out how does the driver and passenger side AC temperatures get disconnected?

The issue I am facing is:

  • Driver side can blow either hot or cold air. The passenger side seems to blow only fan or hot air.
  • There is a mild grinding (not sure how to describe it) sound when I turn the AC system on.
  • The AC exhibits the same behavior whether the Sync is ON or OFF.
  • If the Sync is OFF, and I turn the passenger side to MAX heat there is a single "click" sound (only when it almost reaches the MAX temperature).
  • It does not matter if I am settings the air direction to the Cabin or to the foot area, or both.

This makes me think that the Recirculator Flap Motor (or as it seems to be called Air Distribution Door Motor) is at fault. But I am not sure which motor needs to be replaced.

Below I am attaching the relevant diagrams:

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I'm nearly positive in that system, there are two temperature blend doors, one for drivers side, and one for passenger side. The mode controls (where the air comes from, floor, panel or defroster grill) are common to left and right. Ditto for the single recirculation door.

It's very clear to me that the passenger side temp controller is not working as intended. It's possible that the actuator has a dead motor. It's possible that the actuator internal gears are stripped. If that is the case, it's a pretty easy repair. These electric/ gear driven actuators move a plastic door, varying the quantity of air going thru the heater core. Remember in your system, engine coolant ALWAYS flows thru the heater core. But here's the bad news. It's also possible that the plastic air control door is stripped / stuck. The actuator drive link fits inside door. I've seen doors get split at that point. If that's the case, you will have to remove the air handling unit and repair the door. It's not an easy repair. (Drain A/C refrigerant, drain engine coolant, remove instrument panel, etc...)

temp door actuator

How mechanically inclined are you? Here's a quick test to confirm the specific fault component. I'm guessing if you remove the glove box, and place your hand on the passenger temperature door actuator during vehicle startup you will feel a vibration while the internal parts are in motion. If you change the passenger side temperature while the system is on you will feel the same vibration / grinding. Note, you do NOT need to have the engine running for this test.

In my experience, the most common failure is plastic gears internal to the actuator getting a tooth or two stripped. In the photos you provide, you will be looking at the Right Temperature Door Potentiometer/Actuator & Right Temperature Door Motor. Not sure where you are located (Auto Parts Suppliers?), but if it's just the actuator, the parts cost is pretty reasonable, likely in the $50 USD range for this vehicle.

Note: If for any reason, you do need the vehicle started, please have somebody else start the car from the drivers seat, while you are sitting in the passenger seat for this test... Safety First!!

  • Thank you. PS. as an additional note, the AC blows a gentle fan air when the AC system is OFF. Will look for the part first, and hopefully the fix is the easier one. Will update soon enough. – KingsInnerSoul Jul 31 at 13:07
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    ... gentle fan air... Not sure what that's all about. I do know you need airflow to accurately determine what the interior temperature is for the automatic system to function. Cars I worked on had a really quiet, really small fan dedicated to do that. It worked well, but was expensive. Just running the fan slow would work, too. Do note, the car Heating Ventilation Air Conditioning (HVAC) automatic system will work best if you set everything to auto, and set temperature and don't touch controls again. System knows if you are far away from desired temp, use high blower to get there. – zipzit Jul 31 at 15:35
  • I have ordered a new motor, only to figure out that both the new and old work just fine. Seems that the hand that attaches to the motor and the door isnt openning the door correctly. Not sure how to debug further. – KingsInnerSoul Aug 26 at 22:24
  • Yup, read my comment starting with Here's the bad news... in my answer above. Sounds like you have one of those, and its pretty ugly. Sorry. There is a plastic door, and drive shaft that fits in the end of the door. If the door is split, you need to replace the door inside the HVAC system. Good luck with it. – zipzit Aug 28 at 1:36
  • Thank you for all your tips. I fixed it - I am not sure 100% what was the problem, but I am almost 99% sure that the handle/pin that connects the motor to the door got detached. Reading about it - it seems to be quite a common issue with VW of many models and years. I will post an answer. – KingsInnerSoul Sep 3 at 13:41
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This 2012 VW Passat has two zone AC. The driver and passenger can have two different temperatures blowing at the same time. From my understanding now, the way it works is that the air is constantly being cooled and conditioned. Either the passenger or driver side air is mixed with hot and cold air - by controlling how much a door for the hot/cold air is opened or closed.

That being said, the AC WAS working - because the driver's side AC was successfully changing from cold to hot with no issues. The Passenger's side was constantly blowing hot (or more like outside) temperature air.

There are several issues that can cause this:

  1. The flap (door) that closes or opens is stuck or broken.
  2. The motor that is responsible for opening and closing the mixing door is not working.
  3. The pin that connects the motor to the handle to the pin that plugs into the door is loose.

Case #1 - is the worst case scenario. Case #2 - is same like case #3 - but you will have to get parts. Case #3 - you will not need to spend money on parts.

For both cases #2 and #3 you will need to remove the passenger side glove compartment. According to the Heating - Ventilation and Air Conditioning manual on pages 86-87 (section 6.6), you have to:

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Step #1

First you will have to remove the passenger side trim-panel that goes over the center console as well. It is being held by clips, so you only need a plastic (or any other soft) pry bar or trim removal tool (I bought a set from the local autoshop for about $15, but you can get one on Amazon for less).

Caution: this central trim piece has the Passenger seat-belt light connected to it. If you disconnect this piece, you will have to use a specialized (more expensive than the common OBDII $20 tool) OBDII error removal tool. In order to avoid unplugging it, you can unplug the lights from the trip panel - by unclipping it from both ends.

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In the picture above you can see where (red circles) the trim panel is being secured with clips - as well as the lose Seat-Belt indicator light.

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In the picture above, you can see the (inside) of the trim-panel, where the seat-belt indicator is seated - just move the holding hands sideways to release the indicator light.

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The picture above shows the indicator light on its own, unmounted from the trim panel. It is secured to the trim-panel with these two triangle shaped holders.

Step #2

Remove the soft material from the below of the glove compartment. That soft material is what covers the air-filter housing, as well as the intake/outtake of foot well air. This material is being held in place by two plastic screws. You can unscrew them manually by hands.

Step #3

Remove the passenger side panel. This is needed to expose a screw that holds the glove compartment, as well as give you access to the AC motor unit. There is a single screw that holds the panel. I believe it is a T20 screw.

There is a "hook" on the inside of the panel, that slide in towards the engine. After removing the screw, you can either pull it backwards and down, or force it out - the plastic panel is thin and seems to not break easily.

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Step #4

Remove the glove compartment. There are 8 screws, you will need T20 or T25 screw to undo these. There are 8 screws all together.

To start, remove the side panel using a plastic pry tool. This will expose access to one screw that holds the glove compartment.

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Then remove the screw that we exposed in Step #3:

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Then remove the two screws on the bottom of the glove compartment. In addition, using a plastic pry tool (or a flat-head screw-driver) unclip the leg light (put the pry tool on the left side of the light, and pull it down, it will clip off), then unclip the power cable from the light.

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Next, unscrew the 5 screws on the top and side of the glove compartment.

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At this point you should have 9 screws (all the same) - 8 from the glove compartment, and 1 from the side panel.

Step #5

This step is somewhat complicated. Pull the glove compartment sideways towards the passenger door, and downwards as well. There is a guidepin (big plastic pin) that goes into the central console. need to pop it out, without breaking anything. Once you do that, unclip the 4 power cables. Two that are the same are color coded, so you can mix those, the other two are of a different types, so you cant mix those. Be careful not to break the cables - you can use a small flat-head screw driver to push the plastic holders when unclipping them.

Make sure that the foot-well light cable is removed from the hole, so you wont pull on it when removing the glove compartment.

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The last step is to remove the foot-well distribution plastic thingy, by removing a single screw:

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This whole procedure (Steps #3-$5) are outlined in the Body Interior manual on pages 25-28 (section 1.5):

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At this point, you can check if the handle/pin are loose from the door. The handle is the RED piece in the first two diagrams of this answer. There is a white "hand" that is connected to the motor itself (see in the pictures below), then there is a two-piece black "hand", one end connects to the white "hand", and the other end has a roundish finish (pin) that goes into the door's hole:

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First thing to do at this point is to check if the hands are loose from the motor or from the pin. You can turn on your car, and adjust the AC from MIN to MAX temperatures, you should see the white hand moving the back hand.

Relative positions are marked as follows:

  • LO the white hand is towards the cabin.
  • HI the white hand is towards the engine.

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Make sure the hand is moving, and that it moves the whole black hand, and that the black hand is placed within the pinhole. At this point, if it is loose, just pop it back in. Done.

As far as I remember, when I tried it - the white hand did not move. But when I have released it from the housing (un-mounting the 3 screws) - it worked find. You will have to debug the hands, and motor.

To remove the motor: just unscrew the three white screws (used a size #6 socket), and then remove the power cable.

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Check if the motor is moving the white hand when not mounted. It may move freely now.

One thing I learned is that the motor may seem like it is seized and wont move when you try to move it with your hands - but that motor is well fixed, and will resist your hand/manual force - it does not mean it is seized.

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Note: Without the motor holding the door, the passenger side constantly blows cold (LO) air. Great for the summer days, not so much for chill evenings and cold winter nights.

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Second thing, the passenger size motor is called V159. I had an unpleasant experience ordering it from the dealership. They charged me $170 for it. Ended getting it from AutoZone online. They do not carry it in the store. Paid $134.29 after using a coupon code I found online (regular price is $157.99).

The part arrived from AutoZone and I tried to install it - without comparing the white hand that arrived mounted on the motor. Not sure why, or if I got a "funny" part - the white hand was smaller than the original white hand - and it did not fit. I was going crazy. Compare both the motor and the hand, and use the original hand if needed. (no photos to compare :-( sorry)

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The label on the original part is (you can use it when ordering from the dealership):

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The part I ordered from AutoZone was:

Dorman A/C Heater Blend Door Actuator 604-856

Part Number: 604-856

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To put it all back together, just reverse the order.

The hardest part was to put the glove compartment back in - with the big bulky guide pin. I found that put the guide pin in first, then make sure that the sliding rail on the right side is inside the metal frame, then push in the compartment in. The piece that gives trouble is the lower left (not bottom) screw holding plastic piece (on center console) - it does not easily fit in when trying to slide the compartment in. Don't break it! Use a screw driver or something like that to help and guide it in.

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