My glow plug light flashes (after the engine is started) when the outside temp is in the 40's or below. When the outside temp is higher the engine starts and the light turns off normally. I know the light flashes if there is a bad plug, but why would it only flash when the temp is low?

1980 300SD
Thanks in advance

I am not sure how the glow plug light knows that a glow plug is bad but when it checks your plugs might pass when warmer. This might be a wakeup call for next winter. Check out the resistance of each plug to see.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C