2007 Columbia blowing fuses when brakes applied

Go straight to the brake switch!

 

If the stop light switch was shorted, it would just cause your brake lights to stay on, not blow fuse. Can you ever get the fuse to keep popping right when you install a new one? If you can, I would ohm the fuse output to ground (the side of the fuse not supplying 12v) and see if wire 36B is shorting to ground. If it is, disconnect the turn signal switch and see if the reading goes open. With the turn signal switch disconnected, you will break the circuit to the tail lights and be able to tell if you have a wiring issue going to the tail lights or going back to your trailer cord

 

When you do your testing, make sure your brake switch is either jumped, or you have the brake pedal pressed. The brake switch is in the air manifold, under the cup holder. look for wires 36 on one side of the switch, and 36B on the other side

 

Chip S is some sort of electrical guru - so very technical with the electrical stuff. Keep it up!

 

Could be water in a light.
Or something else wrong inside the light.
I have in the past had to disconnect all brakelights and reconnect them one by one untill i found the one that was causing the trouble.

In that case it turned out to be a bad bulb that shorted inside so there was nothing on the bulb that showed the problem.

 

Great! And to answer your question about the city horn.. no.