if the bulb is good with the key on and engine off check for battery voltage on the small alternator wire at the alternator end of the wire with it disconnected from the alternator.No voltage will mean a problem in that circuit,try to follow that wire back and check wherever you can for corrosion or a break in the wire ,will be a big help if you can locate a wiring diagram for your year/model.If you have battery voltage on the wire and touch that wire to the case of the alt while someone watches for the light on the dash,it should light,if it does check for battery volts at the large wire,if you have correct voltage on the large wire chances are you have another bad alternator.When you resolve the problem please come back with the solution so that we all may learn from your experience. Don

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Red Green "This is only temporary,Unless it works!"

97 E300D 157000 miles
87 300TD ?141k? miles