Electrical Problem?

[Dozerboy]

I started my truck 2x today and it started hard both times. First time was to move out of drive way so it didn't run long. Second time I left it running since the voltage was fluctuating down to below 12V. After 5 mins or so of idling, it was up close to 14V but still fluctuating a little. While truck was idling, I checked the voltage with a digital multimeter, 1 was 13.5 and other was 12.5. They were both fluctuating a little bit. I had 14.2V at the terminal for jump starting. After shutting the truck off, I had 13.5V on the battery reading 14 earlier and 12.5 on the other. The batteries are around 1 yr old. The glowplug light did come on before starting it the 2nd time so the glowplugs could explain the fluctuation. It was about 85 degrees today so I don't know if gridheather or glowplugs would be drawing that much. I have a long trip coming up in a little over a week and want to make sure I don't have any break downs.
Thanks.

 

[tinman22]

check for a lose ground wire. or positive wire for starters. had a buddys truck do something similar about 2 years ago. turned out to be a loose ground wire

 

[jlawles2]

Pull the battery terminals and clean them. You could have corrosion behind them causing the voltage issues.

 

[Dozerboy]

I'll check into those. Today is the first time my truck has seen rain in a long time so it could be a ground. Both batteries where at 12.5V with the truck off not what I had posted earlier. After a few hrs they where down a little some I'm going to recheck them in the morning before I start it.

 

[Sledhead]

After everything is cleaned up and been run for a good charge, pull a battery cable off one and let them sit an hour. Compare volts after that and if they're not real close you could have a dead cell.

 

[Dozerboy]

Load tested the batteries and they are fine so I clean and tighten the connections I could. I will see if that did it I guess.