Charging Mystery (1 Viewer)

[GeoRoss]

TL;DR

Highway trip notice house battery wasn’t charging. At campsite a couple of hours later starting battery registering 12.86V with the car running or not. No charge light came on, but is on with all the other dash lights with the key set to ignition.

Start diagnosing this morning and it is now charging at 14.5V and also charging the house battery. WTF?

Long version. We are meandering toward Durango and currently about 25 miles south of Alpine AZ. Did a bit of recent work that required removing the battery, alternator and alternator bracket. No issues for the past 2 weeks after that work, including new belts.

I tested the fusible links, ign and charge fuses for continuity and all pass that. Wire from alternator to fusible links has continuity. Belts are tight and ECT was below 200° unless flogging it up a hill in +100° ambient temps, so the water pump is pumping. This morning I start it up and it is charging fine. What is weird is the charge light never came on. Very weird.

I’ll order an alternator to pick up in Springerville or Show Low just in case. I have a spare fusible link and AM1 main fuse too. I’m just confused on there being no charge light when it wasn’t charging yesterday.

Any collective thoughts?

 

[alia176]

Ross,

i'll PM you my # and we can noodle it out.

Ali

 

[GeoRoss]

The mystery was circumvented and I got everything charging. Thanks to @alia176 and @Corbet for the help. The house battery charging on a cold engine finally stopped working altogether. This really helped as I was able to identify that the midi fuse feeding the DC-DC charger is what failed. I found a 40A midi fuse in Durango and that was harder to find than I thought it would be. I was also able to kick myself several times remembering the two fuses sitting on my workbench that were supposed to find their way into my parts bag. New fuse and all was good for the rest of the trip.

I went over the charging logs and the peak amperage was 26A. The wiring to the DC-DC charger is sized to handle 80A. I load tested my alternator when I got home and it passed, but this was on a cold engine. I’ll test again when it is hot. I need to check all the grounds and wiring, but my best guess is the midi fuse was either poor or I have a high resistance connection that heated it up. I’ll wait for cool weather before I dive into an in-depth diagnosis. I had no other problems the rest of the trip and I have a Napa spare alternator for next time.