This 2003 Chevrolet Impala came in with the complaint that the battery would go dead after a couple of days of driving. The customer stated that the battery light had been coming on and going off for a while now. The alternator has been replaced three times and the battery twice. The battery light was on, so I checked the basic charging system first. Hooked up my tester.
Cranked the engine and checked the meter. Not charging.
I decided to check the alternator output at the back of the alternator.
Well, twenty plus volts is pretty high. I have seen this problem multiple times on many different vehicles. The cause is an open circuit between the alternator and the battery.
This was the voltage with the engine off. A slight amount of voltage was present, so I was thinking a loose connection. Rather than a completely open circuit caused by a blown fuse or fusible link.
Looking over the engine compartment, I saw that the alternator output lead headed back to the starter. Pretty obvious that there is a problem there. Click on the picture below to enlarge for a better view.
I removed the nut and lock washer so that I could clean the mess up and check for deeper damage.
The ring terminals were arced up but they cleaned up well.
After thoroughly cleaning the ring terminals I found only cosmetic damage. I reassembled the wiring to that battery post on the starter. Installed a new nut and washer.
Check for voltage at the alternator with the engine off.
With the engine on.
I rechecked at the battery with my big tester and all was well, except that the battery was down, as indicated by slightly high amp reading and slightly low voltage reading.
A little time on the battery charger and this one will be ready to go.
Thanks a lot man, was exactly what was wrong with my 2003 impala. I was lost as to what was wrong this changed my 300.00 fix into a .40 cents fix!