GM has a huge problem with repeat failures of their generators caused by an old battery. You might be running into the same situation. Due to the design of their voltage regulator, it switches on and off hundreds of times per second. The ratio of on-time to off-time varies to control the charging rate. Since it turns current flow off instantly, just like in an ignition coil, the coil of wire in the generator creates a big voltage spike. Those spikes can destroy the internal diodes and voltage regulator.
Part of the battery's job is to absorb and dampen those spikes. As they age, they loose their ability to do that even though they still crank the engine just fine. What many professionals are finding out with the GM products is to reduce those repeat failures, they replace the battery at the same time as the generator.
Tuesday, August 9th, 2011 AT 1:13 AM