Lights dim when electrics used.

[fyr145]

Ok then, if you have ruled out #3, then the next thing I would check is the battery then the alternator.

As I stated earlier, get a load tester or you can go to an AutoZone, O'rileys, checker, etc. and have them put their unit on the battery and check it. The load tester simulates having various electrical loads being placed on the battery by them flipping a switch or turning a dial depending on the type of tester then seeing if the battery can still maintain proper output even with a big load draw.

The other test is to check that alternator. just because you see the serpentine belt going around and spinning the pulley on the alternator doesn't necessarily mean that its putting out a charge to the battery. As stated earlier as well, most late model alternators are now built inside the alternator. (I upgraded my stock alternator from the factory 145 amp to a 200 amp because I had added the factory brush AND roof lights.) In the old days, the regulator was a separate unit and if it went faulty or bad, you could simply change out the regulator. Not any more.

The only other issues that I can think of if its still doing it after completing the previous steps mentioned above, is to go on a search for any power wires or connections to your accessories that may be touching or possibly arching on the body. Or worn insulation from being pinched or rubbing on something from vibration. Typically, when these issues occur, it would cause a short and blow the fuse.

Sometimes people tie all their accessories into one power power outlet or line. When all these are being used, the outlet cannot support all of them simultaneously thus causing a voltage drop.

Keep us posted on how the battery and alternator testing goes.