I've been driving a diesel truck for a few years, but I'm new to Mercedes Diesel's...... sure glad there's a site like this!
I've had my 1982 240D for about a week and I've noticed the glow plug lamp comes on when I turn the key to ON, but never goes out. My suspiscion is that the relay is stuck in an energized condition. Tonight after driving for an hour with glow plug lamp on, headlights on and blower motor running wide open, I pulled into my driveway (thank God), shut her off and tried to start her again....... the battery didn't have enough juice to give more than a feeble attempt at turning over. (BTW, the alternator is a known good, but the battery itself is unknown).
I searched "glow plugs" but didn't run acrossed these symptoms. Has anyone run acrossed this? When it's daylight (and I'm done paying for the bills), I'm gonna slap a Fluke to the glowplugs after she's been running for plenty long enough for the relay to de-energize. Just hoping for some insight to read over while I'm at work.........

Phil

be the glow plug relay sticking. it will run batt down in a hurry. can't be too good for the glow plugs either. i would nt drive it that way. there may be a way to disconnect it. i don't know how.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

You can unplug the harness to the plugs at the realay if you think its staying on.

I have a 240D here that has the glow light staying on after the engine was washed. I also didn't mount the relay box correctly and it probably took in more water then it should have. Mine how ever was shutting the plugs off after 40 seconds or so, but the light was still staying on. The car has been driven more recently and the light is staying out almost all the time now.

You will probabaly need a new glow plug relay if all your plugs check out ok.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Johnhef, you mentioned water........ I had just washed her before this issue cropped up.....and then it rained for 3 days. After a few days of dry air, the problem went away. The plugs all checked good and the relay was removing the hots from them after a minute or so, so I'll chalk it up as a water intrusion item to watch out for.

Thanks...

phil

I think you're right in that a little water got in. The light goes out every time on the one I have now. Good thing too, the new owners come to get it on the 5th!

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

I had a similar experience.

Glow Plug Relay

- Patrick

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1982 240D. 198k, Marine Blue/Blue, 4 Speed, Crank Windows, No Sunroof, No Rust, No Oil Leaks
2001 TDI. 197k, Lagoon Blue/Black, 5 speed, Chip, G60/VR6