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Discussion Starter · #1 ·
I've got a problem that driving me crazy. Almost any component of passenger door in my '99 New Beetle 2.0 doesn't work. I'll make the list of these below with description:
  • Speaker - works all good
  • Central lock - doesn' work at any condition, didn't check the voltage
  • Heated mirror and mirror regulation - doesn't work, around 2 volts at power line, doesn't drop when I click the regulation buttons
  • Warning light - doesn't work even if everything is open, no voltage at connector
  • Power window - doesn't work from any side, there is a voltage on connector, but when I disconnect main passenger's comfort module connector I can operate the window by passenger side, but after few minutes it doesn't work again
I did a research and the problem with power window and mirror regulation might be the issue with LIN bus, but I can't diagnose it. I looked over for driver and passenger harnesses all the way to connectors at the bottom of A-pillars but it looks undamaged. I measured low and hi bus voltages on passenger's comfort module and it gives some values but it's probably not reliable since I didn't plug it to osciloscope. I also heard that passenger's side might be affected by driver's side harness.
I checked all fuses, and the power line on passenger's comfort module is always around 12 volt.

Is it damaged comfort module or should I look for damaged harness somewhere else? Does anyone had the same problem?
I'm really mad, it takes much of my time and I want to know what component is the reason of this problem before I start losing my hair.

· Registered
2 Posts
Discussion Starter · #3 ·
It sounds like, you have checked; some of the common power issues in the doors. Just as a reminder, of what we typically see; when a door goes dead: the wiring harness, from the body to the door (flex) portion, will eventually break the wires, killing power to the door. On the older cars, many times; people, will install USED parts, from a different year New Beetle and these parts can fit BUT they are typically different, some even have different pinouts, on the parts themselves. These tend to be: window motors, comfort control modules, wiring harnesses, etc. So, you may not know, the history of the car, be sure to check the part #'s; see, if they are compatible with your year New Beetle and then, there are classic tell tale signs, of used parts, being purchased from a junk yard and the yellow paint marker, markings to identify them for their warranty returns.

If you have a VW specific scan tool; like VCDS by Ross Tech, you can do output testing and view live data, that will tell you the bus status, whether "up or down". The bus will go down; if there is a defective part or the part installed, is incompatible. A full "autoscan", is always the first thing to do; bad electrical parts or bus communication errors; will typically, throw a VW factory trouble code and this, can be a good clue, as to where to start your diagnostic process.

A quick way to check for the bus going down, from a bad or incorrect part; is to do a "hard reset" of the ecu, remove the pos/neg battery cables, touch them together and reinstall on the battery. Many times, this will temporarily, restore functionality to the components in the door and then, in a little while, the bus will go down again, killing the door. If this works temporarily; then, some part, is bringing the bus down and so, detective work, would need to be done, moving forward. I would confirm, the parts are correct; by researching their part #'s (confirm with ETKA or VW's parts site) and then, a process of elimination.

The Ross Tech videos; on VW bus systems, can be helpful, as well:

A good wiring diagram; is always helpful as well, the VW factory versions, can be a bit confusing, compared to the simple versions, which can be accessed from a Haynes manual, online sources like AllData or Mitchell1.

Here are some videos from Ross Tech on reading VW wiring diagrams; the might be helpful as well.

Do you have a VW factory service manual? The eRWin versions, tend to be the best and are geared towards the VW tech at the dealerships. eRWin, can be accessed; through a 24 hour subscription and then, you can download as many manuals as you want.

Otherwise, you might see; if there are some free ones, that are for your particular year and model New Beetle.

Here are some online versions:

So, check things, try the ecu hard reset and review possible issues, like bad or incorrect parts. Report back your diagnostic results, research and visual inspections, we can go from there. Thanks.
So is it definitely problem with bus? The hard reset revived only window regulation for a while. I'll start checking if every component is from 1999 then, do you know any way to manually check which component fails the bus? Disconnecting all of them one by one and checking if everything works is the way of doing it?
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