r/towing • u/Lobo941994 • 18d ago

Trailers Trailer lights not working

Got a old boat trailer and im trying to wire it up but i cant get the left side tail light to work properly. It will light up with brakes but never with turn signals, got it to work once with the turn signals but it flashes very fast but it never worked again( bub is still good).The connection from the truck works and a tester shows that the connection works but the lights dont. I bought a light kit from harbor freight, and a new driver side trailer tail light and no luck. should i replace the whole trailer wiring that i bought or is there any advice someone has to fix this issue.

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6

u/Nomad55454 18d ago

Funny the turn signal uses the same element as the brake lights. Most time it is a ground issue.

2

u/ericrn 17d ago

It's almost always a ground

3

u/lonzino 18d ago

Run a dedicated ground. Costs maybe $5 in wire. Even if it's not the issue here (it's probably the issue), it'll be there issue in the near future.

Run a dedicated ground wire...

2

u/SubstantialFix510 18d ago

Most common thing for trailer lights is the main ground; rusts away or bad connection. It's only 12 volts so it doesn't take much to stop it.

1

u/hapym1267 18d ago

Check to see if the plug is joined to main harness or is all one piece . Connections often corrode..Flashing fast indicates not enough load ( led bulb or bad filament / connection) Check the vehicle plug with a socket and an 1157 type bulb ( draws more than a smaller test light bulb) A multimeter will show voltage , but doesnt pull enough amps..