01.5 24V auto. This has plagued me sense I got the truck. I've replaced the alternator twice and gone through the wiring including the grounds. Being intermittent, it is hard to trace. It occurred most often during startup, but not always like stuck brushes in the alternator, thus the replacements. A code scan shows low voltage with no other codes. Anyone have any suggestions?

 

codes?

What does the multimeter show at the terminals, running, and not?

 

Is the tach working when it seems not to be charging? Also, since the PCM controls charging, you could have a wiring issue going to/from the PCM. If you have a scan tool that lets you control alternator fielding, you can use the scan tool to force fielding and verify the wiring. I don't know if 98.5-02 has a battery temperature sensor, but if so - that can be a problem.

 

Normal battery voltages on battery and cable ends. 12v not running, 14v running. When it fails it is 11v or less and slowly drops. Cables are new. The only code translates to low voltage.

The tach works along with everything else as normal. No battery temp sensor. My scan tool is basic, all it can do is read some codes. The problem is intermittent, so catching it the act as they say is impossible.