I've checked the fuses in the battery box- the 10amp Alt, 10amp LCV, and big 30amp fuses are all ok.

The trucks in the TA shop right now.

Your misson, if you choose to accept it---is to diagnose the problem before they do.

I'm thinking the alt went out.


Oh, as a side not-- the TRailer ABS light always comes on when/while the needle does the swinging wild.

I've driven it 2 nights now- with all the electrical stuff on to try to keep the batteries from exploding.

 

The voltage regulator is shot.

 

Yeah, I had one do that a few years ago when I was still running my dump truck business.

I just happened to get in one of my trucks one day because a driver was sick, started going down the road and noticed the volt meter was pinned!

Voltage regulator was stuck wide open.

Pulled it over and disconnected the hot wire from the alt. and wrapped the terminal with electrical tape so it couldn't short out, then ran the rest of the day that way (summertime, no headlights needed).

The batteries were so overcharged, the gauge was still reading 12 volts at the end of the day, don't know how long the truck was overcharging before I happened to notice it, the driver never reported a problem.

Stuck a new alternator on it that night.

 

I had this happen too. Spiked out for awhile, then fell to like 10 V, then spiked out again, and so forth. Eventually (within an hour or less) the alternator started making very unhappy noises, and it never put out any voltage again.

I was in the middle of nowhere at three in the morning or something, but luckily I had the company's last old fashioned mechanical engine. Screwed in the button and turned off everything but my head- and taillights, and managed to drag her home running the headlights off the batteries.

Dim as hell, but I got there. I bet I'll never do that again as long as I live.