2003 3500 Trailer Wiring 12 Volt Supply

[steam462]

My 2003 Trailer wiring no longer has 12 volts at the plug.

 

I see that this has been a problem. Can anyone tell me where the actual fuse it that supplies this to the harness?

 

On another post I see that road salt caused problems. What was the fix? Replace the harness and the plug at the rear of the truck, or replace the whole harness?

[sonjaab]

You need to put a fuse in Stud #1 position in the underhood

fuse center.

[c4cruiser]

That underhood fuse that protects the 12v to the trailer lug is a 40A fuse. If it has blown, then you need to check out the harness and the connector to make sure there is no bare wire and that the wire is securely attached to the trailer connector.

 

If you see indications of corrosion and/or broken insulation, it would be easier to replace the harness and get a new trailer connector. If one wire in the harness is bad, the chances are that other wires are in poor condition too. It may cost more to replace the factory components, but it beats trying to splice in new wires, wire up a connector and maybe have to repeat the job as other wires go bad.