Tried the search and didn't find anything that fit my issue, so here goes.... Car is a 83 300D

Noticed today that when starting the car cold, the glow plug light came on, but did not go out. No buzzer either. I waited almost a full minute and the glow plug light never went out, so I turned the key. The car started normally, idled smooth, and as soon as it started, the glow plug light went out.

About ten minutes later, while driving, I noticed the glow plug light on. It stayed on for about 15 seconds then went off. About 3 minutes later it was on again for a few seconds then off. This on off cycle continued for my whole 30 minute drive. I shut the car off and about 15 minutes later I tried again.

Engine hot, same thing, glow light stays on until car is started. Glow light again randomly comes on and goes off while driving. Got home and waited 3 hours for the engine to cool before troubleshooting.

Here's the results. After unplugging the harness at the glow plug relay, all five plugs read at .8 ohms. Battery voltage of 15.55 volts is going to the glow plug relay, and at both sides of the the strip fuse (actually there is no strip fuse....the PO removed it and put a heavy gauge jumper wire there)

So, basically the system checks out, but why is the light staying on and no buzzer, and then randomly coming on while driving?

Glenn

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)