After a week or so of some noise coming from the belt drive system, I started to get a battery fault light on the dash, in conjunction with low voltage indicated by the Gap IID Tool during my drive to the office, which is about 10 min. I was seeing 11.1, 10.7, etc. I picked up a freshly rebuilt alternator from a trusted used LR parts dealer. I had a local shop swap out the alternators. They charged up the battery, and tested the system. Showed charging 14.2, and cold start 14.9. Over the next few days I made 4 short trips, each about ten min in total. We have cold weather in the northeast right now, so the morning trips to the office also involved a warm up period in the driveway, about 10-15 min. The drive to the office is 3.5 miles. On the 4th trip after about 2 miles, I got intermittent battery fault light on the dash, followed by the dash and nav system all turning off. I was’t sure at this point if the truck was still running, as the tach was bottomed out. I pulled over, and then realized the truck was still running. Turned off the truck, and started up again. Almost all the fault lights on the dash were kit, suspension fault, transmission fault, nav system and dash shut off for a moment, then come back on. etc. Basically all system failure. Plugged in IID Tool, and limped the truck the next mile to the office. Voltage was showing 16-18 volts. Not good.

Any ideas on what could be causing this high voltage?

 

Often times the negative battery cable is bad. It may look good, but it is corroded on the inside. Voltage may show good, but it will not carry enough current to charge up or run the car. I would look there first. In particular, look at the place behind the battery where it mounts to the fender. Clean that up and check things again, once the battery is charged up.

Hope that helps.

Jeff

 

I'd also suspect that rebuilt alternator.

 

All codes pulled from the faults indicate high voltage. The battery is charging fine. The charging system seems to not be regulated properly. The voltage seems to rise with acceleration.

 

Try best stop driving that thing, you already pushed voyages into a very bad area. The main ECU regulates the alternator output. I doubt its the issue. I put my money on a bad rebuild but I will add that there is a 3-wire connector that is very prone to damage was swapping alts. Amazingly I have done a few alt swaps without issue but people say the plastic is brittle and the connector breaks. I have a spare connector just in case. This 3-wire connection is where the input to the voltage regulator comes from. I never really though what would happen if that connector is not attached. The alternator, in theory, should not exceed 15volts on its own. But maybe that connector broke, came off, etc and now the alt can sorta "run wild"? One would think it would default to a lower output. Maybe I can dig up some details in the manual.

 

Well, this was useless for helping....

 

I’m curious to see if that connector is still ok. Will report back.

 

Replaced the rebuilt alternator with an OE one, and everything is back to normal. Thanks everyone.

 

Replaced the rebuilt alternator with an OE one, and everything is back to normal. Thanks everyone.