Trailer Electrics - Advice Needed (Rear Tail Light)

Most likely there is a short circuit somewhere in the tail light circuit in the trailer's wiring, which will be causing the car's fuse to blow.

To test this, get hold of a digital multimeter (a cheap DIY shop one will be fine), and set it to continuity mode. With the trailer not plugged into the car, Take the bulb out of the right hand tail light, and test between the contacts in the holder - if there is a short the meter will buzz. Check also at the plug end between the tail light connection and the common return.

It's then a case of trial and error to track down the location of the short - it may be, for example, that the wiring has chafed on the frame of the trailer and worn through the insulation.

The photo you've posted doesn't look had enough to cause a failure, but it might be worse inside the bulb holder itself.

Thank you. I've conducted the test, and there is no buzzing on the corroded part. If I test the contact at the top of the picture (that is clean and does not blow the fuse). I get an audible buzz.

I have tried the opposite tail light and I can get an audible buzz on all contacts.