Will one bad plug cause the indicator to not light? I am trying to figure out why the glow plug indicator light won't work. I've had the car for almost 8 weeks and have yet to see it light up. It lights up when I jump it off of the controller plug harness. When I turn the key to the "on" position I get voltage out of all five controller glow plug pins, and can feel when the controller shuts off. I get voltage at each of the five plugs. I have not pulled the plugs and tested them out of the car yet, it's been kinda wet around here lately.

Thanks in advance
Rickf

You can check the plugs without pulling them with a ohm tester. Just pull the plug at the relay and check the resistance to ground at each wire with the key off. The wires going to the GPs should test about .4 ohms or less.

BTW I am not familiar with the '88 but on the '83 it take two GP burnt out to flash the light and more than that to keep it from lighting. Sounds like you might have a burnt out bulb.

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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

Simple way to test this is to unplug the 5 prong plug in the gp relay (the one that has all the cables going to the glow plugs) and turn the key to the on position. If the light comes on, it means one of your glow plugs is possibly bad due to a mismatch in resistance. If it doesn't glow, you have a bad bulb.

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Jason

00 Subaru Legacy (fun wagon)
96 Nissan Sentra (disavowed)
82 300SD (garage queen, will run again hopefully)
87 300DT (Gone: 10/15/2010)

Turns out that one bad glow plug was all it took for the indicator light to not work. Someone cross-threaded the captive nut on #5 and snapped the stud.