Car has been sitting in garage for a few weeks while I've been driving my other cars. Temp is about 50 degrees here in Central CA. Went to start car tonight and turned key but got no glow plug light. Turned engine over a few times, then tried again, but won't start. Didn't try too long, as I wanted to get in here and read on the forums.

Seeing many articles where the GP light will intermittently come on after engine is running, which indicates a bad plug, but not seeing any articles for my model where the light is not coming on at all. Makes me suspicious of the relay, but don't want to spend that $100 if it is something else.

What diagnostic should I be doing next? Car was working fine before I parked it a few weeks ago.

By the way, in warm weather climates (it is quite warm here in Bakersfield most of the year), are glow plugs even necessary? Evidently they help a great deal when temps are below 60-70 degrees.

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Treiberg's Collection: 1981 240D, 1985 300SD, 1992 300E, 1997 E300D, 2005 C230K