R129 Electrical Gremlins-No wipers, SRS light, flashers inop...

[atomix8]

Hey folks, long time member on the Diesel side, finally pulled the trigger on the R129 I've wanted since I was 7 years old.

Let me know if I should move this over to the Tech forum.

1999 SL500 from the south, very nice condition, bought with the convertible top puking hydraulic fluid. Everything (else) worked when I bought it. On the 900 mile drive home to Maryland, the wipers won't work and it's raining heavily. Then the blinkers only indicate left, no matter the position of the stalk. Noticed the seat, steering wheel and mirrors will no longer adjust. Sometimes the stereo would turn off when using the blinkers. High beam flashers don't work. Cool.

Got the car back to MD, pulled all they hydraulics for a Klaus rebuild (just installed them), and started tackling projects on the car. I did a lot of searching, and found a good number of others with similar issues, see my crosspost:
https://www.benzworld.org/threads/srs-light-wipers-headlights-indicator-stereo-seats-problem.2380937/

A lot of these issues seem to happen on my 1999 model year, but I have yet to see a definitive solution. I bought two used convenience relays, have cut open my original to look for issues, but I still have the same symptoms. When I try to use the wipers there's a small groan from the relay. With all this fiddling around, I did get the wipers to work briefly once...and then not again. So I believe the wiper switch and motor are functional.

I have also tried removing fuse #13 (for the convenience relay). This will allow the blinkers to work like normal, the SRS light doesn't come on (at all, it's on fuse #13), but the wipers won't work either. Oddly, if I try to use the wipers without #13, the blinkers go back into left blinker only mode for a few seconds or clicks of the blinker...and then will return to normal operation.

What should I be looking at next???

[bkc]

Not sure if all this applies to 1999 models, since 1999-2002 saw many electrical changes. I'm basing this on my experience with the 1990-1998 models.

If you have had any moisture or water issues, definitely check on as many grounds as you can. Very prone to corrosion. Also, the seat control units are in a recess on the floor under the seats, so can have water pool there (not sure who thought having an electronic module be on the floor, in a swimming pool-like recess, in a convertible that might get rained in...). Make sure to check the fusebox in the trunk, too (right side, towards the top, when looking in from the open trunk lid). Have seen lots of corrosion issues with the fuses in the trunk from moisture vapor, also affecting the unit under the trunk panel, next to the spare tire.

I wish you good luck. Electrical gremlins can be a nightmare to track down in an otherwise perfectly good car. Given that it is a 99 with the newer modules, maybe a good scan tool will be able to help trace back to a problem source.

-Bruce

[atomix8]

Bruce,
Appreciate the reply. I rechecked the trunk areas, and examined under carpet a bit when I replaced the hydraulic cylinders. I saw no evidence of water at all.

I was hoping to not have to start checking every ground on the car, especially as almost all of the ones on this circuit are behind the dash. I have seen zero evidence of water intrusion on this car even after it sat in a few heavy rains in Florida. Though, I suppose I left out the fact that these issues did show up AFTER it had sat outside in Florida rain for a week.

Any suggestions of where to start? Short of ignoring the issue . I have found wiring diagrams, but of course there are three miles of wire in the car.

Should I move this over to the Tech Help section?