w124 weird voltage issue
 

I bought this 92 300e the other day and ran it around (before, during and after purchase) for a bout 2.5 hours. only thing i noticed was a mild stumble once or twice but that was it. didn't use it yesterday but did
start it to see if battery was holding charge. it seemed to be fine.

today i start it (raining since yesterday) and warm it up for 10 minutes and everything is fine. pull out of the drive and it stumbles hard but then goes another 1/4 mile running ok but then dies.
try to start and nothing (no crank), but the tach needle jumps up to 5k rpm when i turn the key. go back an hour later and it starts up and makes it home.
now i can start it and it runs for 2-3 minutes before the abs light comes on and the blower comes on (climate control is set to 'off') and it dies.... plus the power seat doesn't work when this happens and the battery acts as if it's dead.
wait for 10-15 min and car turns over fine and starts but then the abs light comes on after a few mins and it dies....
is it possible the ovp is getting damp due to the 2 days of constant rain (otherwise why did it not act up the other day)? or is some other gremlin at work??

one thing is as your revcounter is on the moving it is telling you that the Crank Possition Sensor is ok . Check broken earth lead from engine to bell housing or check all earth points clean them up and grease them at the same time.

Any time I hear tach and ABS, my assumption is that the OVP is bad. Despite what the manual may say and what you may read here, the only valid test for an OVP is to replace it with a good OVP.

Agree with optimusprime, go over all earth/ground connections. Run additional ground jumpers to see if it helps. My experience is, the less sense an electrical problem makes, the more likely it is a grounding problem.

What is the battery voltage? Is the charging system OK?

battery was dead when i first went to see it (jumped easily) and is really low today......i'm gonna try a new battery and see how that works

In April I took my newly purchased 93 300E to the testing station in the pouring down rain. The same thing happened as I tried to pull into the testing station. I opened the dist cap to find a bunch of carbon build up. I did a regular tune up and she ran like a champ! I also changed out each fuse to copper/ceramic during the process.

i was about ready to do an alt upgrade and had ordered the 0 gauge wire.
i found the 150 amp alt (and a 110 amp from a r129) but they looked different from each other.
also neither seemed to have the voltage reg on them so i decided to look at the one on the car. while i was looking i noticed the small wire was broken from the connector.
i reattached it and now i have all the dash lights back when the key is on and the following voltage readings:

13.48 at idle w/ nothing on
13.22 at idle w/ lights on low beam
13.15 at idle w/ high beam and full defrost blower

that seems like it may have solved the issue....what do you think?