GM has had a huge problem with their generators since they were redesigned for the '87 model year. Due to their design they develop big voltage spikes that can destroy the internal diodes and voltage regulator, and interfere with engine sensor signals. The place to start is by having the charging system professionally load-tested for maximum current and "ripple" voltage. If the most current you can get is exactly one third of the generator's rated output current, (as in 30 amps for the common 90 amp generator), it has a bad diode. One third of the rated current is not enough to meet the demands of the electrical system under all conditions, so the battery will have to make up the difference. Ripple voltage will also be very high when there's a bad diode.
It is common to go through four to six generators in the life of the vehicle. To reduce the number of repeat failures, replace the battery at the same time unless it is less than about two years old. As they age they lose their ability to dampen and absorb those harmful voltage spikes. The old battery may work fine in an '86 or older model.
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Tuesday, August 27th, 2013 AT 2:24 AM
