I have an issue with a 1997 300E glow plug system. I’ve tested the glow plugs from the wire harness and they all appear to be good. I’ve replaced the glow relay but the light still doesn’t come on. I’ve tested the voltage from the ignition switch to the relay and get 7 volts. Anything else that would make the relay not come on? Battery is good and charged.

I had a relay related trouble code on my '97. Glow plugs were fine and the relay looked good inside. I found that the bulb for the glow plug light was burned out. A new bulb solved the problem.

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'97 E 300 D

The car doesn't start so a burned out bulb isn't my problem unfortunately.