Brake and turn signal light out.

[gpfishingdude]

I found out that the right brake and turn signal light were out on the boat trailer when I got home yesterday. This has happened before but not often enough for me to remember, right away, what causes it. The culprit is the #3 position 7.5 amp. mini fuse in the fuse box under the hood on the old F350. The #1 fuse is 7.5 amp. also and it is for the left brake and turn signal light. These fuses don't effect the lights on the truck, just the ones on the trailer.

 

[bruceb58]

You likely have an intermittent short in that circuit. May have to do some detective work to find it. Have some one hold the brakes on the truck and manually move the wire along its path from the connector to the rear right to see if you can blow the fuse. Make sure you watch the brake light while you do this.

Alternatively, disconnect the vehicel from the trailer and use a meter that has an audio continuity tester. Connect it between ground and that circuit, remove the light bulb in the rear or unplug that light and do the same thing. When you hear the beep, you found the short. You have to remove the light from the circuit when you do that because you will have continuity through the bulb.