I've been dealing with electrical problems in my 300D since the summer of '08 thought at first it was alternator. changed that out. Problem returned found some spliced wires to the glow plug light and seatbelt light disconnected those. Running great for a month and all of a sudden radio headlights heater go from not working to working.

I have converted the car to run on WVO and today for the first time when I turned on the WVO pump things would work for 35-40 miles and then it would quit. Had the electrical short issues before converting the car.

Any ideas.. could it be a short in the ignition switch?

It "COULD BE" lots of "Things"... The only thing you Know/Can Prove is an
Intermittent Anomaly (It might even be the Electrical portion of the Ign. Sw.)

1.You need to return the Electrical Wiring to a Stable State (As per MB)
2.Pick up an inexpensive DMM (Digital Multi-Meter) [on Sale] at Sears,
Harbor Freight,Pep Boys,Autozone,Etc.,Etc.
2a. Do an "Advanced Search" on this site...You're looking for the Wiring
Diagrams (or the ETM - Electrical Troubleshooting Manual.).

'Can't find it here ?

3. Call the Classic Center:1-(866) MB Classic [1(866) 622-5277] M-F 9-5 ET
and order the FSM for your model (It might even be Paper,instead of CD)
'Cause without the Wiring Diagrams...You is LOST.

(Unsolicited)
Now, Can I Tell You What I Really Think?

I surely do hope the Professionals (Volunteer or Paid) who provide
Fire Protection in your Area are "Top Notch"...'Cause you may have
need of their services...Sooner than Later.
Electrical Fire onset Can Be Rapid...

I'd not even Park that MB under a detached carport (Much Less inside a Garage).
I'd not even insert the Ignition Key Without a couple of ABC Type extinguishers at hand in the Passenger compartment.
In Fact,I'd disconnect the Battery Negative Cable from the Negative Post,
Until I KNEW WTF was going on.




"Crab Au Gratin", no. 1st you got to learn to catch de crabs.

__________________
'84 300SD sold
124.128

Have a multi meter. I dont no where to begin wiring seems overwhelming to me.

thanks for the info i do have a haynes manual not sure if that would be any help

About all you can do is go over the car, inch by inch, especially in the engine bay, under the dash, in the console, etc., looking for damaged wires, poor connections, no insulation, etc., and fix them as you find them. And take CI's advice: keep a couple of fire extinguishers handy and don't park in a structure. Finally, consider buying a quick release for the battery cable.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970