Golf MK4 Power window problem!

[Bonkerzbanks]

Hi! I drive a Golf MK4 130 TDi. The drivers side window has just stopped working so I've decided to fix it! All other windows work fine. When operating the switch, there is an audible click of a relay switching on then off. The motor doesn't even attempt to move.

The fault code suggested that the electric window motor was faulty so I opened the door panel and took off the motor for examination. I managed to unclip the PCB and housing from the motor connections and putting 12V on the contacts of the motor whizzes it around like it should. No motor problems here - so much for fault codes! (Well, to be fair it is the first ever diagnostic I've done on any car - ever.)

Next I checked the relay on the PCB which seems also to work just fine - contacts close and short as they should - both directions.

So now I decide to check the power supply at the door controller connector and this is where it gets wierd. (See attached diagram 1) On a multimeter, the voltage shows a steady 12V. An attached lamp illuminates. When the motor is attepted to be actuated, this voltage drops to nothing (lamp goes dark!). Then after an indeterminate amount of time it comes back to life by itself.

I'm guessing that this supply pin for the lifter motor is not a direct battery connection but somewhere goes through a current limiter circuit and I suspect that it is this circuit that is defective. Either that or its just a very bad connection somewhere.

My question is does anyone know where this limiter circuit is or where this supply pin connects to? The current flow diagram suggests it's on track "251" but I think I probably don't understand these diagrams as I have no idea how to locate track "251"...

Any help greatly appreciated!

Paul

[Bonkerzbanks]

I finally got around to looking at this again with a view to tracing the wire backwards. The strange electrical behaviour was caused by an almost entirely corroded supply pin on the other end of the door harness. (see picture no. 1). This pin is probably particularly sensitive to corrosion as I think it is live all the time.

I went to a VW dealer to ask for this connector and socket. They had some REALLY funky software in there to locate the part number. Eventually I was told I could get the plug for the door harness but I couldnt have the other part (socket) without buying an entire wiring harness for the car! Seems a bit crazy to me.

So I fixed it with bullet plugs (see picture no. 2).

The only worry is the car is only 2003 so what's the state of the other connectors and why did that one corrode? The panel seems to have a bit of rust on it too so might have to ask what to do about that!

[Boardboy]

Good that you got it fixed Paul. You have got to ask yourself why that plug is so corroded. It must be getting wet some how. Your fix might suffer the same fate if you can't find why. Where does the plug actual live?
regards Boardboy

[Bonkerzbanks]

That's a good point. It wasn't obvious to me how it was getting wet and it didn't seem to feel damp. The connector used to sit in a plastic carrier which cliped into the metalwork. To relieve stress on the modified wiring harness I decided not to use this but when I pulled it out I saw one of the holes was rusty so I'm wondering if the wetness gets in through there. If so, there must be another hole on the outside somewhere. :(. I'll rip it open tomorrow and have a closer look.

Do you know - Is there something I should do to any rusty metalwork to protect it? Location of connector is quite close to the floor behind the trim panel shown in attached pic.

[Boardboy]

Check the rubber boot between the door and bodywork make sure it's fitted properly. Is the bonnet pull that side? If so check the grommet in the engine bay for proper fittment. Sunroof drain in the door shut as well.

As for treating the rust I've not had to do it for a while. But clean it back to bare metal. You can get corrosion treatments from some where like halfords and the paint again.

regards Boardboy