Pete 379 with Electrical Issues

What is the voltage at the batteries and alternator when running? What have you checked so far? Do the gauges work? What do they say (volts/amps)? Knowing the year might be helpful too.

 

CK.ground wire from frame to eng.an ALT.

 

If the batteries have 13.5, then it's charging. What does it do when it "runs out of electricity"? Any W/S or cab leaks that may getting water on the fuse panel?

Check voltage at fuses with circuit loaded. Turn on lights, heater motor, etc. Then check voltage at those fuses to compare to battery voltage. If you have more than few 1/10's of a volt difference, then there is a bad connection to the fuse panel.

Check all grounds and battery connections (at the batteries and starter). I'm not sure which year they started, but on the left side above the starter, you may have a mega fuse that feeds the fuse panel. Check connections in that little box.

 

Check voltage across all fuses and relays in fuse box--the 379 fuse panels--(down at left foot)are rather well known for water leakage over time---you may have to take entire panel out--and check behind--but you may very well find evidence of some water leakage--we have had a few nighhtmares of our own over the years---one suggestion tho--if you find it in/around ANY of the relay--dont bother to try and redo wiring to relay plug---we have found just jumping past the actual plug in--putting bare connectors on the wires and plugging relay in directly(thus bypassing plug in at panel)is easier and yields better results
Good Luck

 

Open the fuse box and turn on the dash lights. Start wiggling relays. It's a common problem with the relay spades not making good connection. If you find one making the lights flicker or go down pull it out and bend the spades out a little and put it back in.

Rough roads in the winter can play havick on connections. Always start with the easy cheap stuff.

 

If you have not found the problem it might be worth checking the low voltage disconnect it should be on left side of dash and hard to get to but you can unplug the big battery cable to it and just plug the two ends together and bypass it