Headlight Warning Buzzer

Something I really miss from modern cars is a beep telling me i’ve left the headlights on when I open the door. As we’ll be venturing further and further afield, anything to prevent a dead starter battery in the middle of nowhere is a definite bonus. Luckily, the T25 has everything ready for this easy low cost modification.


The buzzer is wired in between the fused Blue/Grey cable which powers the dash illumination (switched on and off with the headlight switch) and the courtesy light pressure switch in the door pillar.

As the Blue/Grey wire only receives power when the headlight switch is turned on, the buzzer will only sound when the lights are on and door is opened (grounding the pressure switch).

Parts List

Parts for headlight warning buzzer modification


The pressure switch is secured by a phillips screw, I undid this and pulled the cable out slightly.

I then chopped the brown earth wire and pulled it through to behind the dash*. Next, I fed the new black earth lead through and crimped a connection on. The brown earth, black lead and buzzer negative were then connected using the Wago 3-way block.

*There are 2 holes in the rear of the pillar which are positioned slightly higher than the switch. There is one tiny and one larger hole (I routed through the big one). If you put your hand around you will find them eventually. (Thanks to Dave Hayler on the VW T3 ( T25 ) Knowledge Exchange group for helping me find it).

Buzzer wiring with Wago connector

When I fitted a Switchable USB Socket the Blue/Grey wire connection was left unused (originally it powered the LED). I decided to run the buzzer positive from this plug instead of splicing into the cable elsewhere.

Positive lead connected to dash Blue/Grey wire

The other side of cable is attached to the buzzer positive via a 2-way Wago connector.


Finally the new crimped connection is pushed onto the switch and screwed back into place. I secured the buzzer and Wago connectors behind the dash.



A quick and easy modification which costs £4. Here’s the buzzer in action:

7 thoughts on “Headlight Warning Buzzer

  1. Hey, great article. I am trying to do the same. I can find where the blue grey comes out of the back of the dash and have verified its only live when the lights are on. Where about did you hook into the blue grey – did you chop it at some point and put a 3 way connector in?


    1. Hi Billy, as I’d previously removed the cigarette socket and replaced it with a USB socket (see my other post) the connection for the LED illumination was left available so I used that. You can splice in anywhere really.


  2. I found this answer recently and works perfectly. Buy a wiper relay No99 and fit into slot 10 after removing the Little metal contacts bridge then fit buzzer relay No292 in slot 7.
    Both relays cost £37 (secondhand) but I now have intermittent wiper and lights on warning when ignition off. You do need to remove a little white plug on the steering column to allow the wiper stalk to move down.


  3. Hi,
    Just wanted to say thanks for a great how-to, I kept leaving my lights on and was looking for something exactly like this. I went to Maplin but some connectors and a buzzer and had it done in less than half an hour.



    1. The brown cable is connected to the door switch which earths the connection when open. When you cut the brown cable to take the switch off you then put it in the wago connector.


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