240 1993 electrical issues with brake failure light etc.

240Dad · Post by **240Dad** » 20 Jul 2009, 06:15

My 93 non turbo 240 is coming together. I do have some electrical gremlins that I need help with. I am looking for a common cause on the following:
1. Brake failure light comes on when I touch the brakes even though it is obvious that the brakes work.
2. If headlights are on, Brake failure light stays on all the time.
3. The shift indicator light that shows whether you are in Park, Reverse, Drive, etc. only comes on when I touch the brakes.
4. The chime for open doors comes on when I open the glove compartment and when I turn on the dome light.
Can any of you folks who have worked on 240 electrical issues point me to a common cause or do you think I have multiple issues?
Thanks,
Bill

Post by **billofdurham** » 20 Jul 2009, 12:14

Having looked at wiring diagrams until my eyes are working independently of each other and knowing from other posts that you have had the instrument cluster out I would suggest that you check the large, round connector on the rear of the instrument panel. It would seem to be attached in one way or another to all of the items causing trouble.

Bill.

240Dad · Post by **240Dad** » 20 Jul 2009, 12:18

Thanks, Bill,
I will take a look and let you know what I find.
Bill

240Dad · Post by **240Dad** » 27 Jul 2009, 10:05

Bill,
Upon further investigation I found that the light that keeps coming on is not the "brake failure" light but is the light that comes on when you have a brake light burned out.
I determined this when I pulled the connector from atop the master cylinder resevoir and jumped from one side to the other. That is when the "brake failure" light came on. I checked all brake lights and they are good.
I had the dash out again and couldn't find anything out of the ordinary. It is an integrated unit so I am not sure how to do much to it except make sure all the bulbs are good.
It seems that all of my issues are associated with the circuit controlled by fuse #8. Looks like the power goes from the battery, through that fuse and mainly then to the rheostat that brightens or dims the dash lights and the shift indicator light at the shifter. I plan to chase these wires and see if there is an obvious problem. Can you offer any advice on how best to do this?
Thanks,
Bill

Post by **billofdurham** » 27 Jul 2009, 11:40

The bulb failure sensor is very sensitive and can detect the difference between an old bulb and a new one. The general recommendation when replacing bulbs is to do it in pairs. It can also detect the difference between the silver coloured and the gold coloured metal on the bulbs - apparently the resistance is different.

If you have replaced any bulbs covered by the bulb failure sensor - low beam, tail lights and brake lights - check for the above.

You will find that fuse #16 covers parking lights (right side), instruments and control panel lights and shift indicator light. Fuse #8 covers central locking, interior and glove compartment lights and trunk compartment lights. I realise that the diagram I posted appears to show only fuse#8 but that was only one page of six and covered the instrument panel. If you would like all of the pages let me know.

Bill.