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UK-POLOS.NET - THE VW Polo Forum • Driver's side door voltage issue
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Driver's side door voltage issue

Posted: Tue Oct 06, 2026 6:02 pm
by firebulletz
Good evening everyone,

I have an issue regarding the voltage at the driver's side door (Polo 6r 2011 1.6 tdi).
I installed an under-door light using the following two connections:

- Green/white wire from the door lock connector
- Red/yellow wire from the window regulator connector

When the door opens, it supplies 12V; when closed, it drops to 0V.
After a few days, I noticed the light had stopped working. I tried replacing the LED bulb, but it still didn't work. Today, I took it apart and tested it with a multimeter: instead of 12V, I'm getting 5.88V, and that 5.88V reading remains even when the door is closed.

What could be the cause?

I was planning to connect an LED to illuminate the interior door handle and a neon strip by drawing power from the window switch, but I'm worried about running into further problems.

Years ago, I tried installing a neon strip but used a 5V version, which didn't work properly. Now I plan to get 12V ones, but I want to resolve the current issue first and understand if adding lights to these circuits might cause long-term problems. I'm not sure if I need to install something in between to prevent voltage drops or other issues.

I'm attaching a photo to give you an idea of ​​the neon strip installation.
https://imgur.com/a/oiNcq5y


Thanks.

Re: Driver's side door voltage issue

Posted: Wed Oct 07, 2026 2:45 am
by ciclo
If you performed the installation as indicated here:
viewtopic.php?p=488807#p488807
the F2 driver's door contact switch—located within the F220 driver's side central locking unit (VX21 driver's door lock unit)—may be failing.

Also check the connections you made for this installation. Look for possible points where the wires you added are damaged.

For any interior light you wish to add that should only be ON 'at night' (i.e., when position/side/parking lights are active), you must use a relay triggered by the 58 or 58d signal, powered by a +30 supply.

Never use the 58 or 58d signal (which is dedicated to lighting switches) as the power supply source, only as a relay activation signal. Whether due to a lack of knowledge or other, more mundane reasons, it is common to use the "58" signal as a power source for this type of electrical installation... and that is when strange things start happening with the instrument cluster, the radio, the climate control panel, etc.🤭

Re: Driver's side door voltage issue

Posted: Wed Oct 07, 2026 9:17 am
by firebulletz
Hi Ciclo,

The problem is the lock mechanism "5K1 837 015"? I need to replace it


Can you recommend a relay for the interior lights I plan to install later?
While we're at it, is there a diagram showing where to get the 58d signal, the positive, and the negative to connect the relay and lights?

Re: Driver's side door voltage issue

Posted: Wed Oct 07, 2026 6:11 pm
by ciclo
To determine if switch F2 is faulty, use a multimeter to test the switch 'correctly' according to the diagram (checking for 12V or 0V), or also with a good diagnostic tool like VCDS.
First, clean and lubricate the door opening and closing mechanism if necessary.

This switch F2 is the only element that intervenes between the WRM power fuse and the ground of the F220 driver's side central locking unit.

It is preferable to use original 12v LED lamps to ensure that it is not the lamp itself that is ruining the installation you did.

---

A good relay for an ambient lighting or additional interior lighting setup (LED strips, etc.) is the VW646. You can physically mount it in the relay carrier-BCM bracket. In addition to supplying power to the new installation, it isolates the original installation of interior lights from the new installation.

I remember setting up an ambient lighting system like this for a good friend -forum member- when he asked me to make the wiring looms for automatic lights, HBA, etc., although I never created a diagram to share on the forum— to avoid as much as possible creating threads of non-original installations with all types of lamps or LED strips (+ additional devices -dimmers via bluetooth-wifi, etc-) coming from parallel universes.
It is actually quite easy to do once you have a clear plan.

I have several threads in the forum where I share the erWin pdfs with original diagrams and maintenance for 6R and 6C. Look for them and create your own custom installation.

Re: Driver's side door voltage issue

Posted: Wed Oct 07, 2026 6:22 pm
by firebulletz
The multimeter reads 5.88V with the door open and closed. So, do I think it's defective?

Do you have a code for the original LED lights?

---

Perfect, thanks. As soon as I have all the materials, I'll look for them :D

Re: Driver's side door voltage issue

Posted: Wed Oct 07, 2026 6:29 pm
by ciclo
To help us look up and find the part number for the original LED 'lamps' you'll first need to show us the holes you made in the door panel.

The voltage readings you indicate are inappropriate—or should be impossible—if all the components in the door are functioning correctly.🤷‍♂️