[2cheap4dealer]

Hi everyone,

I'm slowly working my way down my Passat repair list and hit something that hasn't worked the whole time I have owned the car. I have always had some sort of short in the trunk. When reading through the forums, some people mention the actuator and others the latch. Given my list of symptoms, which seems more likely?

1. Trunk will pop open with the key fob.
2. It will not open with the trunk button inside the glove box ('99). You can hear the relay for the button clicking, but after several attempts it blows fuse #14.
3. Replacing the trunk light bulb with the trunk lid open immediately shorts fuse #14. I believe I repaired all of the solder joints on the floor unless there is a split towards the back of the car.
4. At no point has the trunk open light on the instrument cluster worked properly.

Thanks in advance!

 

[AndreasPassat]

Had a very similar problem on my wife's 2003 GLX. Her car has that stupid wing on the trunk lid which was obviously installed some time after the car was new. The mounting point in the center section has a missing gasket, over the years water has leak through the trunk lid at that point and ran down on top of the trunk lid liner right onto the trunk lock release mechanism. Using the key was extremely difficult, it felt like the key was going to twist off while turning it to release the trunk. Trunk button didn't work either, would blow fuse. Turns out the mechanism was completely corroded.
Replaced with another used mechanism in perfect condition, problem solved.

Depending on model of your car you might have the manual release lever inside the trunk, if so, and if you need to replace the lock mechanism, make sure you get the right lock assembly. It only took me three tries to get them to send me the right one.

Both trunk release lock mechanism types can be interchanged on the car no matter the option.
But if you have the manual release option, I would keep it. You never know if you'll need it, especially in todays mental society.

 

[2cheap4dealer]

Thanks for the tip! Sorry about the late reply-slowly getting back into my car after having back surgery. I'll take the lid apart when I get a chance and keep you posted

 

[FrescoGreen01.5]

<snip>

1. Trunk will pop open with the key fob.
2. It will not open with the trunk button inside the glove box ('99). You can hear the relay for the button clicking, but after several attempts it blows fuse #14.
3. Replacing the trunk light bulb with the trunk lid open immediately shorts fuse #14. I believe I repaired all of the solder joints on the floor unless there is a split towards the back of the car.
4. At no point has the trunk open light on the instrument cluster worked properly.

Thanks in advance!

Reference Bentley schematic 29, assuming your car was manufactured August '98 or later.

(1.) The trunk unlock motor is powered from fuse 38 via relay 79, which is controlled by the CCM. When you unlock via the fob, the CCM just energizes the relay (by grounding pin 86, one side of the coil). And since that works for you, it's not the problem.

(2.) The trunk button, when pressed, grounds a CCM input, which would cause the CCM to energize the unlock relay, just like the fob. If the CCM wiring has been repaired, I'd have to wonder if that wiring is wrong or shorted to another pin, etc.

(3.) I can't imagine how installing a light bulb would blow a fuse... the socket has two wires: the red/black is the +12V; it connects to the CCM output that powers the makeup lights, dome light, reading lights, and puddle lights (do they all work?). The brown/black wire connects to the "unlocked" switch, which grounds the wire when the trunk is unlocked (typically energizing the light). The brown/black also connects to a CCM input and the cluster to provide the "trunk open" indication. This design is typical of our cars--the switch simply grounds the wire, so that an accidental ground won't blow a fuse... Again here, a miswire in the CCM wiring repair is my only good theory to explain your issue.

(4.) As per 3 above, this cluster input just needs to be connected to ground to light the light. It's the brown/black wire.

A good troubleshooting first step might be to access the trunk lid actuator and unplug it, then ground the brown/black wire. That should cause the cluster indicator to light (with key on, probably). If it doesn't, that says your trouble is in the floor wiring, not the lid actuator.

After that, you're probably in to the CCM wiring/repairs, which may not be doctor recommended after surgery...

Do you have the Bentley manual and a multimeter?

 

[2cheap4dealer]

Sorry it took me a few days. I have a multimeter and VCDS, Santa didn't bring me the Bentley I was hoping for, and IIRC it was manufactured in June of '98. The dealership initial inspection date in the front of my maintenance book is early July.

 

[FrescoGreen01.5]

2cheap4dealer, your car's manufacture date means we should be looking at Bentley schematic 13 instead of 29, but I don't see any differences that affect you.

I did notice there are two motors: V151 Motor for unlock rear lid (controlled by relay 79) and V53 Decklid Central Locking System Motor (powered directly from CCM). V53, being powered directly from the CCM, could conceivably blow fuse #14 if it's bound up. It's not clear from the schematics exactly what all is part of the trunk latch, so if you tear in to it, post a photo. (My Passat sedan was a facelift version, so it did not have the second motor.)