I'm having a very odd issue with my #3 fuse (inside vehicle). Whenever I plug in my trailer lights and I turn on my headlights my #3 fuses always blows - dash lights, cluster lights, and tail lights.

Has anyone had this issue before?

 

you likely have a short in the wiring in the trailer. Give the wiring a good once over

 

Will do. I'll take a volt meter and see what I can find. I'll report back.

 

Volt/OHM meter

Leave trailer light wire disconnected

Look here for standard wire color chart for trailer lights: How to wire up the lights & brakes for your vehicle & trailer

Brown wire is used for Parking/Tail lights

Turn on parking lights and test brown wire on truck trailer wiring connector
Should see 12volts(battery voltage, 12.3-12.8volts)

Switch meter over to OHMS
0 OHMS = a short
Now Ground one of the meters probes to the trailer bare metal
Put other probe on Trailers Brown wire(tail lights)
Should show 20+ ohms
0 ohms(or under 5 ohms) means that wire is shorted to trailers metal somewhere

Could be in a light fixture or wire is damaged somewhere
Boat trailers often get shorted out light fixtures because of being dripped in the water all the time, salt water is the worst

Also make sure Trailers wiring connector matches up with trucks connector, i.e. brown truck wire is plugging into brown trailer wire


A fuse is just a softer metal wire, when you power up anything it will have some "resistance" to power flow, the resistance is the OHMs, resistance also slows the AMPs being used
At 0 ohms, no resistance, then all the AMPs available can flow out, with a car battery thats about 400amps, lol, and that of course would be a bad thing
Fuses are used to prevent 0 ohm short from pulling all AMPs available
When a fuse blows it means OHMs are too low somewhere in that circuit

 

Thank you very much for all the information. I'm going to go test the trailer either later today or tomorrow. I will report back with the solution

 

Sorry for the late response. I was able to locate the problem. I have a 4-round male adapted coming off of the trucks harness. I have a 4-round female plug on my trailer that I use. I bypassed this and hooked up my trailer directly to the truck's harness. Fixed the issue.

Using my volt meter I was able to find out that the 4-round male adapter on the truck is wired incorrectly which is casing the short.

 

Good Work

Thanks for the update