hey guys, I have low voltage on my gauge in the truck, like 9 or 10 with it running. I used a voltmeter and checked my battery, it has 12. Then I put the meter on the positive of the battery and the negative in the fuse box where the alternator wire is and was reading 14.3, so my alternator is working..when we put it on the battery negative it was only 12. Any ideas? I have a feeling a few grounds may be in the wrong place...would that cause this?

 

Was the truck running for all these measurements? Are you using the same ground point?

They should all be reading the same voltages. Things are wired in parallel. If you have a lot of corrosion on terminals it can change the readings. Try cleaning the battery posts. It is also not uncommon for the cables to corrode under the insulation so they look good.

While cranking the engine, measure the voltages from one end of each battery cable to the other end. You should not have more than a .6v drop. That'll check the cables. Clean all ground points as well.

 

yes, the truck was running. The battery is brand new and the wires are good to go. I am not sure what is causing this...before I pulled the engine it was fine. Beside the ground wires I am sure the wiring is spot on.