BMW E36 Blog

Turning Your BMW Lights On Automatically At Night . . . Main light

11th April 2008

Turning Your BMW Lights On Automatically At Night . . . Main light


I wrote six articles until now about how you can make your BMW lights turn on automatically at night. I will summarize these posts for you in case you have missed them. In the first post, I proved that this should be something easy to implement inside a BMW E36 car. In the second post, I presented a circuit diagram that will help you create the electronic circuit that is supposed to control your lights and turn them on automatically when it gets dark. Of course, if you don’t know how to implement such a circuit or you simply feeling too lazy to do it, you can ask some electrician to do it for you. I’m sure he will agree if you paid him $20. In the third post, I wrote about my first attempt to implement this circuit and told you that it’s partially working but it needed some enhancements. In the fourth post, I created a video with the circuit implemented on breadboard and connected directly to my brother’s car lights. In the fifth post, I soldered the circuit on permanent board and showed you exactly how I intend to use it inside my car. In the sixth post, I posted 4 videos that I shoot while testing the auto light system. In case you didn’t see these videos I suggest you check them first before proceeding.

Aright, today, I decided to solve the last problem that I’ve mentioned in the last post, which is main lights problem. I didn’t know previously which wire(s) I should use to turn the main lights on using the auto-light circuit, so my car used to turn the angel eyes lights and the dashboard lights on automatically at night, but not the main lights. As you can see, this is good, but it’s not good enough. So, I decided to try and solve this problem today. To do that, I looked in my Bentley manual and I found the lighting system diagram for the BMW E36. I finally found that I should use the yellow wire to turn the main lights on, so now it should be a very easy task. Take a look at the new wiring diagram for the auto-light circuit. The new modifications are in red:

Please notice that I’ve introduced 4 diodes to get 4 wires out of the relay to be able to control:
1. Left angel eye light (yellow/gray).
2. Right angel eye light (purple/gray).
3. Dashboard lights (black/gray).
4. Main lights (yellow).

The diodes should serve as a precaution measure to prevent the interference between the 4 parts mentioned above.

With this new information, I thought that I’ve figured the solution to my problem, so I decided to go out and connect it to see if it’s going to work or not.

For some reason, when I connect the fourth controller to the yellow wire (main lights), the circuit started to make a buzzing sound (resulting from the relay being switched on and off very quickly) and the headlights turn on and off very quickly too. I’m not really sure about this problem and how to solve it. So, I’m going to review everything I did. The only reason I can think of right now that is causing this problem is that the relay is not suitable for the headlights some how. I’m going to try another relay with larger current limit and see if this solves the problem. If you guys have any idea why this is happening, I would appreciate your comments.

As you can see, this is still unfinished work, so if you want to implement this in your car, I suggest you wait until I figure out the solution for this problem to avoid paying for parts and work that is not proven to be 100% successful yet.


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posted in Do It Yourself, Electrical, Technical Info, Uncategorized | 8 Comments