What specifically do you have for battery voltage with the engine running? What kind of problem are you trying to solve?
GM has had a real big problem with their generators since the '87 model year. Due to their design, they produce huge voltage spikes that can damage the internal diodes and voltage regulator and interfere with computer sensor signals. When you need to replace the generator, to reduce the high number of repeat failures, replace the battery at the same time unless it's less than about two years old. As they age they lose their ability to dampen and absorb those spikes.
Besides testing for proper charging voltage at the battery, which should be between 13.75 and 14.75 volts, you need a professional load tester to test for maximum output current. If you have a failed diode, all you'll be able to get is exactly one third of the generator's rated current. 30 amps from the common 90 amps generator isn't enough to run the entire electrical system under all conditions.
Friday, March 28th, 2014 AT 5:31 PM