Making a thread to document my findings on a recent battery drain with my '83 300D

I found that my car has a battery drain after it left my wife stranded at work. Brought it home and charged the battery over night and it worked fine until a few days after (which was yesterday). I had the car apart replacing the steering box and when I went to start it the car would crank slowly and not fire. Darn, dead battery again. Charge the battery and the battery won't take a charge.

Now thinking back this has occurred a few times in the past where the car would drain the battery while off, recent past to be more specific but I thought my wife left something on or it was the battery going out.

So I just bought a brand new, $150 battery ( I recall these not costing more than $110 ). Car cranks up just fine and I start tracing out the electrical system.

Fuse by fuse I still see 12v across the negative terminal and terminal connector. Then I get to the glow plug relay and disconnect both connectors and the voltage reading goes to zero.


So I am now under the assumption the glow plug relay is to blame. Current work around is to unplug the relay when parked and plug back in when driving it. My wife drives all of 1 mile to work so she will be fine with it plugged in.

tomorrow on my lunch I am hitting up the junk yard since they have two diesels in their inventory and a GP relay is $6. Hopefully one of the two relays is still there so I can test this theory.

I haven't dug deep enough to find out if I can crack open the relay and find the fault / repair it.

stay tuned for more exciting finds!