13.4 is just a little below the acceptable range. I'd like to see it somewhere between 13.75 and 14.75 volts. Measure right across the battery terminals while the engine is running.
This is a real poor design generator. It is common to go through four to six of them in the life of the vehicle, but what many professionals are finding out is the repeat failures can be reduced by replacing the perfectly good battery at the same time. The old battery will work fine in a 1986 or older car with the good older design generator. The newer style develops a real lot of huge voltage spikes that are normally dampened out by the battery. As batteries age they lose their ability to dampen those spikes. That can lead to running problems from interfering with sensor signals, and those spikes can destroy the diodes and voltage regulator inside the generator.
Thursday, March 31st, 2011 AT 4:48 AM