Measure the battery voltage while the engine is running, but use the AC scale, not the normal DC scale. This GM generator is by far the worst pile ever produced and causes a lot of running problems due to very high ripple and voltage spikes that they produce. It is very common to go through four to six of these generators in the life of the vehicle. What many professionals are finding out is to reduce the number of repeat generator failures you must replace the battery at the same time. As they age, they lose their ability to dampen and absorb those voltage spikes. Those spikes interfere with the signals from other sensors and confuse the Engine Computer. The old battery will work fine in an older pre-1987 car that used the much better generator.
If you measure more than one or two volts of AC voltage at the battery or at the generator's output terminal, try a new battery first. If that doesn't help, have the generator load tested on a tester that measures ripple. If the ripple is very high, suspect a defective diode inside the generator. If one of the six are defective, you will only be able to get a maximum of very near one third of the generator's rated capacity. That means you'll only get about 35 amps on a load test. Most newer generators are capable of delivering 90 - 120 amps.
Friday, May 27th, 2011 AT 7:20 AM