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My 2012 VW Passat SEL has dual AC Zones. The driver's side is working fine. Hot and cold air. However, the passenger side AC is blowing what seems to be the outside air (on the really hot days it blows really hit air, and at night it blows not such hot air, but not cold air). When i turn on the AC on cold i hear a mild (hard to describe but sounds like a hissing) sound coming from the passanger side front area when driving in low gear.

I have been told it is possible that the flap that moves the air is broken, or the passenger compressor is broken (are there two compressors?).

I do have the cheap OBD2 (OBDII) scanner but it gave me no information about the AC system. Would AutoZone or a similar store scanner be able to pin the issue?

In reality, what would be good troubleshooting ideas/steps? Any ideas on a fix?

  • There is a button on AC control unit "DUAL" or "SYNC". Does the problem you mentioned repeat when the button is on/off? – coner Jul 11 at 14:49
  • @coner the passanger's side AC is never blowing cold air (unless its cold outside) regardless of the dual or sync setting. – KingsInnerSoul Jul 11 at 14:56
  • I don't think the car has two compressor. But maybe using wrong coolant clogged the system. Have you changed the coolant fluid recently? – coner Jul 11 at 15:06
  • @coner i haven't changed coolant. And they won't do that during an oil change either. – KingsInnerSoul Jul 11 at 15:10
  • @coner thinking about it, if the system is clogged, wouldn't that mean that both sides wont be producing cold air? In this instance only the passenger side is not cooling. – KingsInnerSoul Jul 12 at 21:07
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Please refer to a similar question I asked here:

Air distribution map of a 2012 VW Passat?

The answer for both questions is as follows:

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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