I have had an intermittent issue with this for a long time, but now it seems it is a permanent issue. The glow plug dash light will not come on, and vehicle will not start - so I am sure glow plugs are not getting any juice.

I have replaced the glow plug relay - no effect.

So what else can I troubleshoot? The glow plug relay has one big wire (probably the 12V line) and the glow plug connector to the plugs and then a smaller connector with two wires on it. I am guessing that the small 2-wire plug is what delivers the signal for the relay to come on, so maybe I should check voltages there? Does it connect back to an engine module? If the glow plug relay is good (which it is), then is the engine module the culprit?

Thanks in advance for any help!

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