On my 85 300D I started to have some crazy problems which I have tracked down to the glow plug system. I noticed while driving that the battery voltage would drop to 11 volts at night (12.5 volts when the headlights were not on) for a couple of seconds to what seemed like a minute and then the volt meter would pop back up to it's normal voltage of about 14 volts. I have traced this down to number 1 and 2 glow plugs coming on at arbitrary times. When it seems to do this is erratic so it took awhile to find this problem. I expect the alternator at first until I installed an amp meter inline with the alternator and noticed that when the voltage dropped to 11 volts the current from the alternator went up to 60 amps output.

I placed a volt meter on each glow plug and sure enough it was only 1 and 2 that were getting voltage with the car running and they would periodically go on and off. Everything else seemed to act normal. The light on the dash did not come on when this happened. If I turned the key to the start posistion but just jogged the starter and let the key go back to the on position the glow plugs would turn off which seemed normal but the other two periodically coming on was Freaky. So I ordered a new relay.

I got a new relay in the mail that I paid $119 for, it's made by Bosch out of Malaysia and It's worse then the old one. This relay won't turn off at all. Even after 45 seconds in the on position it will stay on. After the car has started it will stay on for what I timed up to a 1.5 minutes before I turned it off. This really made me scratch my head, question my sanity and choice of religion. I am looking for some confirmation from the folks on this website, but I think I was sold a bad relay. For now I have put the old unit back on. By the way I have check the plugs. I am getting about 0.7 to 1 ohms at each plug. Has any one else had a relay fail in each of these ways?

TimK

Sometimes a glitchy electrical portion (the part behind the tumbler) of the "ignition" switch will make intermittant contact because of looseness inside and start the glow cycle over and over again. FWIW

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

How cold is it where you are at the moment?

newer glow plug relays "afterglow" for longer than the early ones. It may be perfectly normal if it's cold enough outside.

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Alex.

MB Tech
Sydney, Australia
Volvo 122S
W201 190D 2.5 manual
W202 C240
W203 C32

At the time a put on the new relay last night, it was 45 degrees F in the garage and the engine was warm to the touch but not hot. I wasn't aware of the new relays having any afterglow. The MB shop manual doesn't mention for my year of vehicle (85 3000D). Staying on for a minute seemed way too long.

TimK

several members have posted here reporting that their new glow plug relays have been disappointing, operating the glow plugs way too much and burning them out in short order. I decided against trying one and am staying with the original for that reason.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

can anyone tell me how to tell the two different types of glow plug relays apart? part #, size, shape, steve 83sd

Remove the housing from your old glow plug relay and see if there's debris inside.

I had an intermittant glow plug relay problem due to water sloshing around inside my glow plug relay.

Hope this helps you.

- 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

I really didn't want to wait two more days for mail order or to run the risk of my old unit buring a plug and there by dorking a cylinder so I went to the dealership and bought a MB genuine relay. The dealer charged me $174.00 (and no tax, thank you Oregon). Considering the brand new bad unit I got from parts-on-line.net for a $119 plus overnight shipping, I thought the dealer price was reasonable. The unit I got from the dealer works great. Will put a few mile on it on the hiway and see how it holds up.

TimK