How would you do that?

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1988 300SE 83K+
1991 350SDL 283K+

a 12 volt bulb like a turn signal bulb, one lead to a glow plug, the other to ground. Test the brightness of the bulb on the battery first, then watch the brightness across the glow plugs when glowing, it should be slightly dimmer. If it is very faint, then you have battery or connection problems.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Got it. Man, that's going to be fun. Them little buggers are hard to reach.

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1988 300SE 83K+
1991 350SDL 283K+

Tape the lead to a long screwdriver or long rod (no electrical contact to the screw driver).

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked