Weird. I drove to a friend's house last night and when I came out to the car, the battery was totally dead.

Headlights were not on. My only guess was that somehow the glow plugs stayed on the last time they were energized. It is a new (3 month old) AGM battery with lotsa capacity, so to drain it dead over a few hours would take a big load, like glow plugs.

I am running a manual glow plug contactor with a momentary pushbutton (all from mercedes source). I can't imagine the big contactor would stick- but anything is possible I guess.

I plan to run a pilot light from the glow plugs so that I can see if they are on when they shouldn't be.

Any other ideas?

A bad battery.

I brought my 300 D down to Mexico a few years ago. I had a good working Bosch battery with some years on it. I decided to outsmart myself and put in a new battery. I bought a new Bosch and drove the car here. After about a year the battery began going dead intermittently. It would be fine for weeks, and then overnight go dead. I checked everything. Finally I gave up and bought a new battery. End of problem.

Richard

Is it possible that the alternator isn't charging the battery? If you weren't running the headlights, it's possible that the voltage dropped pretty low and went unnoticed since the diesels don't really use electricity for anything once the engine is running. If so, when you went to restart, the glow plugs probably killed off what charge it had left.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I'll check the alternator output tomorrow. But it works some time at least because I drove home after a jump start got me going, and the battery was fully charged after the drive.

get a new battery w at least 800 cca cold crank amps

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Carpe Diem!

I am not sure what an AMG Battery is but I read some where in an article on Bosch Voltage regulators that there is some newer Batteries that need more then 13.75 charging volts in order to charge them.

This was with an old battery. I drove to a realiatives house. Stayed over 1.5 hours got in the Car and started right up.
I stoped at a Taco Bell just long enough to buy and got into the Car to Start and nothing happend.
I had a volt meter with me and I had the 12.50 Volts.

I tried to use a Jumper Wire down at the Starter and I barly got a spark. I was getting voltage but little amperage. My best guess was the Battery was damaged internally.

I walked across the Street to an Autozone and Bought another Battery and after that was installed it started right up and was charging properly.

That was on My Volvo Diesel but it has a similar Bosch Starter.

The Glow Plug Relay was a Ford Starter Solenoid and a spring loaded rocker switch.

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84 300D, 82 Volvo 244Gl Diesel