temps got pretty low last night so i plugged in the block heater. i noticed when i started the car that the glow plug light only stayed on for a few seconds, when normally below 40 degrees it stays lit for 10 or so seconds.

it was the roughest start i have had in a long time. is it possible that the temp sensor for the glow plugs was misinformed by the warmer coolant and only let them burn for a few seconds?

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'92 300D 2.5
'99 E300TD

Yep

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Jim

Not sure what the answer to your actual question is....but I don't think that the block being warmed to the degree that it is by the block heater would substantially reduce the time needed to glow. Those idiot lights can get pretty unreliable over time.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k 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