Mysterious electrical problem w124 - PeachParts Mercedes-Benz Forum

Phillytwotank · #1 02-10-2016, 10:35 PM

Hey y'all,

Asking for your input on diagnosing and an electrical problem.

'92 300d w124

Most of the time everything is fine no symptoms of the problem at all
Sometimes for no apparent reason the problem will show itself.
Tach,temp,fuel and oil pressure gauges will all start "cutting out"
Also can hear the seatbelt buzzer sounding faintly

Any ideas to get me pointed in the direction of getting this figured out will be appreciated.

Thanks

andrewjtx · #2 02-10-2016, 10:36 PM

OVP going bad?

Phillytwotank · #3 02-11-2016, 06:40 AM

I've never looked into diagnosing OVP relay problems. Will look Into that.
The problem also seems to be correlated to stapling on the brakes. As in, it will go from showing some readings to showing nothing when I depress the brake pedal.

jay_bob · #4 02-11-2016, 09:41 AM

This is screaming "Ground problem"

Do you have the schematics for the car?

vstech · #5 02-11-2016, 09:49 AM

Mine started doing that when the alternator was going south...

have the alt checked. and test the battery, and all the connections while you are at it!

Phillytwotank · #6 02-11-2016, 01:19 PM

Yeah, ground problem. I thought about that. Still haven't had a chance to go underneath to check out the grounding "strap". I assume that it's a similar setup as a w123.

I don't have any electrical schematics for this model. Is there a good source for those out there somewhere?

Alternator... Nothing is impossible at this point I guess but I'm pretty sure the alternator was replaced just before I got this car last year. Looks new. Not sure. Could have it checked fairly easily I suppose.

jay_bob · #7 02-11-2016, 02:00 PM

Schematics at Model 124 Maintenance Manual Index

Along with the rest of the 124 FSM

Startek was not working last time I checked a week ago.

mannys9130 · #8 02-11-2016, 02:08 PM

X2 for ground fault.

It wouldn't hurt to run a starting charging and battery system test at an Autozone. Make sure your variables there are within tolerances.

bricktron · #9 02-11-2016, 03:47 PM

ground problem! don't miss a strap, there will be a number of them. also, an intermittent circuit due to cracked solder within the cluster is another possible cause. on the W123 it has been recommended to add another ground strap there for security. good luck.

123mike · #10 02-11-2016, 06:31 PM

I put an alligator clip to a wire. One end to a screw behind cluster , the clip to a frame part. Boozanger. Fixed

Phillytwotank · #11 03-09-2016, 08:14 PM

Seem to have gotten it sorted out. Took the main ground cable off and cleaned a bunch of white powdery stuff off of both sides. Have not had the problem since.