My 2008 E320 Bluetec is showing a figure of a glow plug in the car clock, the same one that illuminates before starting the engine.
This illuminates and goes off just after starting the car but it comes on again and stays on while the engine is running.
I try to find more information in the Mercedes Benz Owner Manual but not found this specific one.
This light goes on and goes off without any change in the car performance. The car start and run normally.
What is the reason for this light coming on after engine is running? Some glow plug going bad or some already bad? Or any other reason?
Thanks for your help.

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Nyck - TX - USA

If there is one someone can post the startek factory service manual site and there would likely be a better description there. Also a better description of what the codes mean.

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84 300D, 82 Volvo 244Gl Diesel

In all probability you have one glow plug that's bad. Pull the codes...simple OBD2 will work for this.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Beware they revised the glow plugs on a 642 to a different voltage. (No it’s not straight 12 V)

This may require changing all 6 plus the controller.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

This morning starting the engine, the light came on and went off as it is supposed to work. Driving for 28 Miles the light did not came on again as it was doing earlier.
In the afternoon after driving for about 10 miles the light came on again and staid on for the rest of the trip, about 18 miles.
I then stopped at Autozone and had it scanned and a code: P0670 was found.
Code says: Glow Plug Module Control Circuit
Went home and now will start the engine back again tomorrow morning and see if light will go on or not.
Any suggestion after this update?
Thanks everyone.

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Nyck - TX - USA

I never heard about voltage be not straight 12V
Thanks for that

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Nyck - TX - USA

Same behavior as our ML320, whole story here

http://www.peachparts.com/shopforum/diesel-discussion/367295-om642-glow-plug-replacement.html

The plugs are rated for a voltage less than 12 V. The controller fires the plugs with PWM (Square wave with varying duty cycle) which keeps the plugs from burning up. It applies 12 V but since it’s switched rapidly the plugs can take it. If you try to test these with straight 12 V they will die quickly.

MB did reissue the glow plugs for the gen 1 642 and changed the voltage from what was original in 2007-2009. It’s necessary to do all 6 and change the relay.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Unfortunatly they are using the glow plugs for another function than just engine starts. This was not the smartest design approach.

The glow plugs are expensive and cdi type engines need very little assistance from glow plugs to start. Complex with extreme reliability I personally do not mind. Otherwise it usually sucks.

The wives Volkswagon Passat has expensive glow plugs. As far as I am aware they are just used for engine starts when it gets cold out. Possibly not active at all in most months of the year.