MKIV door locks explained - why you're having problems!!! :(

[VgRt6]

MKIV DOOR LOCKS EXPLAINED !!! ...

Since so many people with '99.5-'01 MKIV cars seem to be having trouble with their door locks not working properly (also prevalent in B5 Passats), I thought I'd put together a quick explanation about how the locks work in our cars and why there's been so many problems. People with the newer and quieter door lock mechanisms should not have the problems described in this thread - the problem appears to be fixed in these modules.

If your door locks behave like their from another planet (e.g., a door doesn't lock when it's supposed to, the car doesn't recognize a door's been opened, a door automatically relocks itself even when it's open and sets the alarm off ... the list goes on and on ...), then you know exactly how frustrating this problem is. Personally, I'm sick of having to double-check that my driver's door has actually locked - that's why I did a little investigating about what's going on.

Unlike door locks in older cars which are relatively simple mechanical devices along with a separate plunger switch to determine if a door is open or closed (kind of like on your fridge), the door locks in recent-model VWs are complicated electro-mechanical devices with everything (latch, microswitches) in one relatively compact unit or 'module'.

Here are some pics which should help explain what I'm talking about.

The picture below shows the rear edge of one of the doors on my 99.5 Jetta. The only part of the door locks that is visible is the latch mechanism that hooks onto the u-latch on the b-pillar.

Unfortunately for us, this means that VW put the entire door lock mechanism INSIDE the door. To do any kind of work on it, you need to take the inner door panel off and then remove the window regulator carrier panel. The door lock module is attached to the inside of the carrier panel and is also secured to the edge of the door (by the two 8mm triple square bolts in the picture above). If you remove the carrier panel and door lock module from the door, you'll see the following. The door lock module is indicated by the red arrow.

The two images below show the front and rear sides of the module after it's been disconnected from the carrier panel. The red arrows point to the cable that connects to the interior latch used to open the door, the blue arrows point to the edge of the module that's attached to the rear edge of the door and the green arrow points to the cable that connects to the exterior door handle.

The picture below shows the lock module separated into its two major parts, the electronics portion (circuit board, microswitches, etc) indicated by the blue arrow and the mechanical portion (latch mechanism, cable mechanisms, etc) indicated by the red arrow.

By taking the electronics portion of the lock module apart, it becomes clear that the module uses no less than FOUR microswitches to keep track of the state and operation of the door. Two microswitches (red and blue arrows) are used to detect if the key is being turned in the driver's handle to lock/unlock the doors and open/close the windows and sunroof. A third microswitch (yellow arrow) is used to monitor the state of the locking mechanism, i.e., whether the door is locked or unlocked.

The fourth microswitch is actually in the mechanical portion of the lock module (red arrow in picture below) and is connected to the electronics portion by the red and blue wires. This microswitch detects whether the door is open or closed by monitoring the position of the latch mechanism.

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WHY YOU'RE HAVING PROBLEMS WITH YOUR DOOR LOCKS !!!

... or in other words, why do the locks behave like some demon child conjured up by VW engineers one night after a few too many s at OktoberFest?

It has been speculated for a while now by myself and a few others that the problems with the door lock module was a sticky microswitch - this would explain the sometimes intermittent nature of the problems and also would explain why a good, hard whack to the edge of the door near the lock module would temporarily solve them. After reading the following DIY REPAIR by TaligentX, it's clear now that the microswitches in the lock module are perfectly fine. Rather, the problems are due to poor soldering of the contacts between the pins on the locks module's electrical harness connector and the printed circuit board in the lock module.

The region of interest is circled in red in the picture below.

The reason for the problems with the lock modules is clear in the close-up image of this region below. For some reason (bad solder choice, not enough solder, too much physical movement ... who knows???), the solder joints that connect the leads in the harness to the printed circuits for the microswitches tend to crack over time, resulting in either an intermittent or no connection between the two. I found two contacts cracked - pin#3 (blue arrow) and pin#7 (red arrow). Based on the few cases I've heard about where the module was taken apart and solder joints were cracked, it appears that the joints for pins#3, 5 and 7 are the problematic ones.

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THE SOLUTION !!!

The solution to the problem is actually very simple. Using a low-wattage soldering iron and some solder, all you need to do is remelt the solder joint (to reestablish the connection) and add a small amount of solder (to beef up the connection).

I did this on my Jetta today and the module now works perfectly!!! If only I had know about this three years ago when the lock module started acting up. To make sure that the problem shouldn't happen again, I not only resoldered the joints for pins#3 and 7, but also for pin#5 ... just in case!

If you want to do this on your car, you can use the following DIY to remove the door lock module from your car door ...

HOW TO REMOVE YOUR DOOR LOCK MODULE

As I write this, vasillalov is putting together a DIY for disassembling the lock module and resoldering the damaged contacts. I'll post the link here when it's done.

You can also use the TaligentX DIY to repair the lock module - the door panel removal portion is Passat-specific, so use my MKIV DIY instead.

Finally, here's a case of for TaligentX. We all owe him big time for figuring this out.

UPDATE: (8-20-04)

I fixed my front passenger's door lock module this weekend and found exactly the same thing wrong - pins#4 (blue) and 8 (red) were also cracked. Ironically, this lock module was actually working recently, but gave me problems for over a year a while back.

Between my two modules and the one in TaligentX's DIY, the failures have all occurred on the same two pins (3 and/or 7 on driver's side and 4 and/or 8 on passenger's side). Even though this is only three cases, I'd bet that most/all of the other failures out there are for exactly the same reason. I'd say there appears to be enough of a reason for VW to issue an extended warranty on these parts.

UPDATE: (8-26-04)

I met up with a local Vortexer (melmandc) on 8-24-04 to fix his door lock module. Upon taking it apart, we found that the solder contacts that failed in my and other modules were perfectly fine. What failed instead was the microswitch in the mechanical portion of the module that detects if the door is open. It's the one marked by the read arrow below.

I should have figured this out before removing and opening up the module since his symptoms were slightly different than most. On his car, if you unlocked the driver's door, opened it up and didn't put the key in the ignition or open another door, the driver's door would automatically relock. This is the classic situation that most people experience - the car doesn't recognize that the door has been opened. The thing that makes his situation different is that the lock module WILL lock and unlock whether the door is open or closed, unlike most problems where the lock module WILL NOT lock whether the door is open or closed.

UPDATE: (11-4-04)

I should have posted this info a while ago, but better late than never! The Cherry part numbers for the three small microswitches in the electonic portion of the lock module in the picture below are as follows (info taken from HERE or HERE:

DK-1-G-UL-A0 (red and yellow arrows)
DK-1-G-TR-A0 (blue arrow)

I still haven't found the Burgess part number for the fourth microswitch in the mechanical portion of the lock module. I'll post it as soon as I find it.

UPDATE: (7-30-05)

A fellow Vortexer alerted me to this thread over at TDIClub.com about a cheap fix for failures of the 4th microswitch (the one in the mechanical portion of the module). I haen't done the fix myself, but it looks promising.

http://forums.tdiclub.com/showthread.php?p=730184

UPDATE: (6-13-09)

A friend (Sebich1) was having similar DLM problems to mine, so we opened up his DLM today. Guess what we found. That's right, cracked solder joints, as expected.

Modified by VgRt6 at 9:31 PM 6-13-2009

[bergenvr6]

another great writeup Gary, thanks

[Der Kommissar]

Awesome write up-it seems that the 99.5 cars have a lot of problems with this.

Thanks

[awwsheeet]

seriously gansta

[VgRt6]

It seems like there's problem with some '00 and '01 cars as well. VW mst have received a huge batch of defective parts.

Maybe they'll finally do an extended warranty on the modules like they've done on other lemon parts they've put in the early MKIV cars. I won't hold my breath though. At least mine is working in the mean time now.

Gary

[gehr]

No problems......yet...awesome write up Gary. Vote Gary for President of Vortex in '05

[VgRt6]

No need to thank me, I'm just passing on the info. TaligentX deserves your thanks. And save some for vasillalov - he was kind enough to agree to put the DIY together.

Gary

[Der Kommissar]

Quote, originally posted by VgRt6 »

No need to thank me, I'm just passing on the info. TaligentX deserves your thanks. And save some for vasillalov - he was kind enough to agree to put the DIY together. Gary

for them.

[placenta]

damn great write up.

[Noog]

Cool, my cars got probs with the drivers door lock but I was just too lazy to research it, etc. I come to the vortex and there's a post about it on the main page!

My car doesn't always lock when I press the lock button, and when I go over 15mph it doesn't always lock either.

Matt

[vasillalov]

Gary,
Excellent DIY. Just what we thought it would be!
I will be doing my DIY tomorrow!


Modified by vasillalov at 9:43 PM 8-14-2004

[VgRt6]

Quote, originally posted by Noog »

Cool, my cars got probs with the drivers door lock but I was just too lazy to research it, etc. I come to the vortex and there's a post about it on the main page! My car doesn't always lock when I press the lock button, and when I go over 15mph it doesn't always lock either. Matt

That's what mine was doing. This fix will cure your problems too.

Gary

[DJPark]

Great writeup! I have a 2002 and don't have this problem but I found your post very interesting.

[VgRt6]

You're car shouldn't have this problem. Let me guess, it has the newer, quieter version of the door locks. This problem was fixed when they redesigned the part for the '02 cars.

I just added this info to the original post. It should have been in there all along.

Gary

[Stone20V]

asdkfjasl;f

[VgRt6]

Quote, originally posted by Stone20V »

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[diive4sho]

I wanna go do this right now but i'll wait till tomorrow......my car doesn't notice that my door is open so when i open it no lights come on ....so frustrating at night!!!

[VgRt6]

I know. I don't know how many times in the past three years I've left my lights on because I forgot they were on and the chime didn't come on when the engine was off and the door was opened (the car didn't know the door was opened). Or how many times I had to go back to the car and double-check that the door was actually locked. It feels great to have this problem finally fixed.

Good luck with the fix. It should cure the problem!

Gary

[VgRt6]

Bump.

Gary

[mschaff]

Hey!...don't I get a for pointing out that link...

Just kidding...another nice write up! I'll try this sometime soon...These locks are driving me nuts...

--
Mike

[VgRt6]

Sorry! Actually, you can have a case of too! If it weren't for you posting that link, MANY of us wouldn't know about this fix!

My one question is ... HOW COME THIS LINK WAS ONLY POSTED RECENTLY!?!?!? Was the TaligentX link just posted recently? Or did you just find out about it recently? I wish someone had figured this out years ago. I'm kicking my self for not taking my lock module apart a year ago when I changed my regulator clips.

Gary


Modified by VgRt6 at 11:30 AM 8-15-2004

[mschaff]

Not sure how long ago that link was created. I stumbled upon it through Google when my girlfriend's Golf starting acting crazy...

On a somewhat unrelated note, I have to say I'm pretty impressed with the VW (owner) community. Not being a VW owner myself (although a frequent driver), I found these forums while trying to troubleshoot various problems my girlfriend's very problematic 99.5 Golf GL. I'm happy to say, I've saved quite a bit of money and time by consulting with others on these boards. Despite the problems with VW part failures and the shady dealerships, my next car might be a VW just because of the community.

Well, looks like we got the dreaded P1128 code last night, so a new MAF sensor might be in our future...

Keep up the good work Gary.

--
Mike

[Pifiu]

Great writeup! I was about to replace some door modules for like 110 bucks a pop or more! I understand its not exactly easy to take everything apart, but the actual fix is easy!

Nice post and love you guys for making DIY's!

[DORKEE_BORA_VR6]

i love you

[VgRt6]

Quote, originally posted by mschaff »

Well, looks like we got the dreaded P1128 code last night, so a new MAF sensor might be in our future...

A new MAF will definitely fix P1128. I'd love to know the percentage of MKIV VWs that have had this code. I'm sure it's some ridiculously high number.

Gary

[VgRt6]

Quote, originally posted by Pifiu »

Great writeup! I was about to replace some door modules for like 110 bucks a pop or more! I understand its not exactly easy to take everything apart, but the actual fix is easy!

You're correct. Getting to the door module is not the easiest thing, but the actual fix of the module is simple. Regardless of whether yo ureplace the module or repair it, you still have to do the same amount of work to get to the module, so you might as well save the $100+ and repair the existing ones.

Yesterday I fixed my driver's door module and everything is working normally again. My front passenger's module has acted up in the past, but is now currently working OK. I'm planning on resoldering the joints on it as well just so it won't start acting up in the future.

Gary

[ericthebikeman]

Good write up. I have a question though.

I unlock using the remote then the door relocks after ~30 seconds unless I put the key in the ignition. Is this normal or a problem with the module? The interior lights do come on when I open the door so it should know the door is open right or is that another switch?

Could explain why the memory seats don't move when I open the door.

[SpewingChunks]

i'm impressed- awesome write up

[VgRt6]

Quote, originally posted by ericthebikeman »

I unlock using the remote then the door relocks after ~30 seconds unless I put the key in the ignition. Is this normal or a problem with the module? The interior lights do come on when I open the door so it should know the door is open right or is that another switch? Could explain why the memory seats don't move when I open the door.

I'd say your problem is definitely the module. I'm not sure why your lights come on, but the other symptoms suggest that the door doesn't recognize it's open. I had the same problem with the door relocking unless I put the key in the ignition. I don't have memory seats, but it makes sense that they'd only move when it detects the door has been opened.

The problems with the locks are way too common for your problems to be caused by something else. I'd be willing to bet that doing the fix described above would fix your problems.

Gary

[ericthebikeman]

Good to know. Also the driver door is supposed to stay unlocked when the door is open and you press lock right? I figured it was to prevent myself from locking the keys in the car.

[Delux]

awesome write up. i was gonna fix this on my car over a year ago but never got around to it. tired of getting in the car and having the alarm going off with the door wide open

[VgRt6]

Quote, originally posted by ericthebikeman »

Good to know. Also the driver door is supposed to stay unlocked when the door is open and you press lock right? I figured it was to prevent myself from locking the keys in the car.

That is exactly right.

Gary

[VgRt6]

Bump.

[thatTDIguy]

my microswitch actually broke so this is a no go for me. Off to the electronics store for a similar switch

[VgRt6]

FYI, the three microswitches in the electronics portion of the door lock module are Cherry DK Series - Subminiature Sealed micros. This also the same micro that's used in the trunk lock assembly, except that the locating posts on the side of the switch are not present and a custom actuator arm is used.

The fourth microswitch, the one that's in the mechanical portion of the door lock module is a Burgess micro. I'm not sure what model it is though.

I should probably add this info to the original post.

Gary


Modified by VgRt6 at 7:21 AM 8-20-2004