Most
electrical problems with a FG trailer can be diagnosed with a
$5 HF multimeter if one knows how to actually use the meter.
The problem is that most people don't understand electricity , or how the
electrical system in their trailer works or how to troubleshoot an
electrical problem .
If you read many of the electrical guestion on this forum , that lack of knowledge is obvious . That's why these threads take 6 pages trying to explain to someone how to change a
light bulb.
Byron does make a good point , if you don't know how to test a battery then take it to someone that does and have them determine if the battery is the source of the problem.
We have people on this forum that if it doesn't involve pushing an app on a smart phone are totally lost and find everyday mechanical knowledge as mundane. As long as they have someone to lean on they will never learn to figure it out for themselves.