Jump to content

SOLVED - best process to identify electrical problem?


Recommended Posts

Got home last night and turned off the car. Pushed knob in to turnoff headlights. Headlights turned off but dashboard light* stayed on. The light can dim until there is no light, but not an ideal solution. Guessing the issue is at the point where the electricity is cut off from the dashboard light. I phrase it that way because I have no experience working with electronic systems. 


My questions is, if you didn't have BMW2002faq, how would you go about identifying the problem?  Would also love the answer or suggestions, but want to learn how my car works and how to fix it while....you know.....fix it. 


Thanks in advance,



* Bonus points if you head Meatloaf signing about dashboard lights while reading this post. 

Edited by Devilish_02
Link to comment
Share on other sites

1 hour ago, Devilish_02 said:

how would you go about identifying the problem?

Welcome Jake.


First...get on this BMW2002faq forum!

Second: Tell us about your car (year, model, mods, etc.)

Third: Explain the best you can what issues you are having, when they started, what changed, etc.

Then stay connected to this forum until your problem(s) (relating to your 2002) are solved.

Lots of talent and help available!



Link to comment
Share on other sites

My (somewhat) educated guess is that the variable resistor that controls the dash lights' brightness has run amok.   It's inside the headlight switch, and is nothing more than a resistance wire wound around an insulator.  Turning the light switch knob moves a contact around this resistance wire, varying the voltage going to the dash lights.  When those switches get old, they get cranky, and my guess is that somewhere inside the switch either the resistance wire or the movable contact are boogered up, and  are not allowing the dash lights to disconnect.  The light circuit on an 02 is live all the time (except the headlights on 71 and later cars) so the feed to the switch is hot all the time.  


Best way to check:  find another switch and substitute.  You might also try cleaning that variable resistor with tuner cleaner or even brake cleaner and see if that helps.  But my guess is that the switch is going bad and probably can't be fixed.  


let us know whatcha find...



  • Like 1
Link to comment
Share on other sites

Thanks for all the input. 


As noted above, it was probably the light switch. 


Photo of what the variable resistor looks like. Second photo shows two tiny springs, one of which is somewhere in my garage. 🤬 Thus, going to purchase a replacement vs trying to fix. There is another thread where people discuss successfully repairing them. Not losing tiny springs being a lynchpin for success. 





Screen Shot 2022-11-10 at 12.54.37 PM.png

Screen Shot 2022-11-10 at 12.54.45 PM.png

Link to comment
Share on other sites


On 11/9/2022 at 2:32 PM, Devilish_02 said:

My questions is, if you didn't have BMW2002faq, how would you go about identifying the problem?

Wiring diagrams!  Basically for any electrical problem, you need the diagram for how the circuit works, and from there you can move on to various tests to isolate/identify the part of the circuit that isn't working, and then fix it.  Let's say you have an early Euro 2002, so that diagram would be here:


You find the light switch on it, the bubble 21, and you see that the rheostat for the dash lights gets powered by the Green/Red wire from fuse #2, and then drops the voltage through the rheostat (for the dimming), and then goes to the dashboard on the green yellow wire:


So then you just start checking the voltage at wires and working your way backwards from the lights toward the battery until you find the problem!

  • Like 1
Link to comment
Share on other sites

  • Devilish_02 changed the title to SOLVED - best process to identify electrical problem?

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Upcoming Events

  • Create New...