rstl99

I noticed when I started my truck at the cottage yesterday morning (temperature had dropped and there was frost on the ground), it kind of balked, as if there was barely sufficient voltage to turn it over. It started right away though. After starting, I noticed the voltmeter read low (first line above the 8), and only some seconds later it went up to above 14, where it usually sits. Drove back to the city, all seemed fine.

This morning, when I started it, it didn't balk like yesterday, but similar thing with the voltmeter (low at first then goes up to 14). In addition, I notice now, when the truck is idling cold, that the voltage cycles from 14, down to a lower spot for a few seconds, back up to 14 for more seconds, then down again). I notice the engine rpm goes down when the voltage drops, and comes back up when it rises to normal level.

What could be happening?

rstl99

Upon doing some research, it seems that the grid heater cycling is likely the cause of what I'm seeing. As well, the batteries (one of them anyway) may be getting old and having problems coping with the extra load. I'm still a little new to Cummins, so this is another useful learning experience!

9812vram

That's exactly what it sounds like. Remember - replace both batteries at the same time, even if only one is bad.

rstl99

Thanks! Will do, I plan on taking some lengthy road trips next year with slide-in camper, so two top-of-the-line new batteries will go in there! Truck will be stored for the winter.