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1970 Coupe DeVille, 2002 Eldorado Collector Series
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Discussion Starter · #1 ·
Here's a good one, hopefully this will help somebody someday. This applies to 1970 Cadillac, possibly other years. If your gen lamp is always on when the car is running, and you've checked your charging system and it's working fine, check the gauge/trans fuse. The way the gen lamp works, it gets power from both sides of the circuit, and if there is an imbalance in power between sides, it will illuminate. If the gauge/trans fuse is blown, it's not getting power from that side, so the lamp will illuminate even though everything else is working fine. Be aware that SOMETHING caused that fuse to blow, and this root cause should be tracked down. In my case, I believe it was due to a failing battery connector on the back of the alternator causing high resistance and possibly overcharging.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,738 Posts
It can also be lit dimly and still charge. That is most likely a failed diode trio within the Alternator.
 
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