Start by having the charging system load-tested for maximum output current and "ripple" voltage. GM has had a huge problem with their generators since they redesigned them for the '87 model year. Due to their design, they develop large voltage spikes that can damage the internal diodes and voltage regulator, and interfere with computer sensor signals. If one of the six diodes fails, the generator will only be able to deliver one third of its rated current. 30 amps from the common 90 amp generator is not enough to run the entire electrical system under all conditions but it may be enough to keep the battery mostly charged. The heater fan draws a lot of current and could load the system down to the point the Engine Computer turns off.
It is common to go through four to six replacement 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 voltage spikes.
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Saturday, December 14th, 2013 AT 8:02 AM