This article is from the Fishing bass FAQ, by Bass Rogue with numerous contributions by others.
- Bass Rogue
The wiring between a tow vehicle and a trailer is quite simple. However, when
something goes wrong, this simple wiring can become very complex and confusing.
Here are some thoughts about trailer wiring that might help when the boat is
spending too much time in the garage waiting for you to get a couple of light
There are two approaches to troubleshooting. The first approach is
based on knowing what is wrong. For example, the right rear turn
light stops working. You venture a guess, the bulb is burnt out. You
change the right rear bulb, and the problem goes away. This can be
describe as the "I've seen this problem before" or the "what's the
most likely thing that's broken" approach to troubleshooting.
Finding the most likely failed part is the easiest way to
troubleshoot, but it doesn't always work. What would happen if you
changed the right rear bulb, and the problem didn't go away? Would
you change the light socket, the light fixture, or maybe redo the
wiring? It's often this next step that gets us into trouble when the
easiest way doesn't work. We start "Easter-egging" or just changing
stuff. This can waste a lot of time and cost a little money. It can
also be the source of induced failures which really compound the
problem. In case you're not familiar with the term, an induced
failure is when you break something while trying to fix something
There are two approaches to troubleshooting. The second approach is
based on knowing what is good. For example, the right rear turn light
stops working. You check the voltage coming out of the tow vehicle
and discover it isn't there. Therefore, you conclude, the trailer is
good. You look at the tow vehicle turn lights and discover they work
correctly. Therefore, you conclude the tow vehicle's basic wiring is
good. You remember the other lights on the trailer were working
correctly. Therefore, you conclude, the ground wire is good. About
this point in time, you conclude there is only one wire left to check
and that's probably where the problem lies.
This second approach to troubleshooting is the best approach when you have a
difficult problem. Systematically go at things and keep shrinking the area
where the problem might be - eliminate what is known to be good. Also, don't
assume anything, prove the things are good. Too often, it's the stuff we
is good that gets us.