Hi Guys

picked up a 2000 D2 this weekend, searched multiple forums - brake lights, turn signals, shifter lights work when light switch is off - when light switch is either on parking lights of full on the dash lights dont turn on, the shift indicator lights go off and the rear pass brake light goes out - the pass side side maker light does not go on.

I took apart the stalk switch, cleaned, scotch-brighted, and dielectric greased all the contacts - no change
checked all the fuses - all fuses in engine bay and under dash are good
checked ground at taillight housing and get continuity between the grounds in both pass and driver housing as well as each connector to body


I'm thinking this means the BCU is suspect? should I remove it and try and clean the contacts? are there test procedures that I can work through?

It could also be the dimmer? Ive tried jumping the pins one the three pin connector for it but it doesnt change the lighting

I have a copy of RAVE but to be honest it sucks - my 74 911s workshop manual is better organized and makes more sense than this so looking for a little help

thanks in advance

 

start simple. Check your grounds.

 

okay. Thank you, hoping for a bit more direction than that if possible?


Like I said above I had started at both tail lights and the grounds in the harnesses have continuity to the body and themselves which other grounds should I check ? BCU grounds ? Stalk switch molex connector grounds?

 

Any LED bulbs being used?

I recently had a LED brake light bulb cause all of my marker lights to come on, dash lights, gear selector lights all to come on with the brakes. Then with the lights on the brake lights where all ways on too.

Prior owner had hacked the towing harness and done something really odd with the center brake light too. Those where causing me other issues when I first got my D2.

 

If it were me, I'd start by checking for a trailer harness and then I'd be tracing grounds and wiring for the lights. I'd guess it's something at the rear, but I guess it could be anywhere. This sounds more like a wire grounding out than a BCU issue to me.

Rather than the workshop manual, you might find some helpful information in the electrical library. Before you hit the link - just an FYI that it's a 700 page PDF: https://discoii.files.wordpress.com/...al-library.pdf

 

No LEDs but definitely a trailer harness

so is that adapter/converter a factory piece? I noticed it up in the wheel well when I was testing the grounds on the pass rear tail light harness - thanks for this link - are there specific resistance values listed for that as well?

 

If I remember correctly, the trailer plug was an option that plugged into a harness behind the passenger side tail light. Not sure if you'll find resistance values in the library, but not sure that you'd need them - I would think that you'd be tracing 12v and ground points with a test light and working your way from the bulbs back to the BCU to try and find a failure point.