Trailer lights not working

[acidrane]

A friend asked me to tow his jetski this weekend (we was towing his boat) and upon connecting the 4pin connector, the lights on the trailer were not working. A quick search showed that a brake controller is not necessary for the 4pin connector. I also read about the 30amp fuse that blows out quite often; I cant imagine a 3 month old car would have a blow fuse but I didn't check.

Is there a switch or setting I need to change? The lights worked on his truck.

 

[honda250xtitan]

a bad ground on the trailer will blow your fuse.

 

[Bill Z]

Check the fuse - like mentioned it'll blow if there's a bad ground on the trailer.

Also, check the trailer ground and make sure it's connected and not corroded.

 

[Ascole]

When you say lights do you mean marker lights, turn signals, 4 ways, or all the above?
Easy way to test your 4pin is use a voltmeter on each of the pins.
Trailer wire testing is a little more tedious but definitely start with a bad trailer ground. I ran into a similar issue and after completely tearing out all trailer wiring, I found 12” of corroded wire.


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[acidrane]

When you say lights do you mean marker lights, turn signals, 4 ways, or all the above?
Easy way to test your 4pin is use a voltmeter on each of the pins.
Trailer wire testing is a little more tedious but definitely start with a bad trailer ground. I ran into a similar issue and after completely tearing out all trailer wiring, I found 12” of corroded wire.


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There was no power to any of the lights on the trailer.

I just checked the fuse on my truck and it was not burnt out. I'll have to check my plug and the trailer wiring. I love electrical issues :yuck:

 

[Ascole]

There was no power to any of the lights on the trailer.

I just checked the fuse on my truck and it was not burnt out. I'll have to check my plug and the trailer wiring. I love electrical issues :yuck:

Check the 4pin on your truck 1st, then the 4 pin harness on the trailer. If it’s the 4pin on the 4runner, you can get a 7 to 4 pin converter and go that route till you get it fixed.
My guess would be something to do with the trailer wiring; corroded or bad ground or something along those lines due to the trailer being submerged. Trailer wiring is pretty easy to figure out as there are no fuses or relays of any kind and is essentially 3 power/ground and 1 harness ground.


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[acidrane]

Check the 4pin on your truck 1st, then the 4 pin harness on the trailer. If it’s the 4pin on the 4runner, you can get a 7 to 4 pin converter and go that route till you get it fixed.
My guess would be something to do with the trailer wiring; corroded or bad ground or something along those lines due to the trailer being submerged. Trailer wiring is pretty easy to figure out as there are no fuses or relays of any kind and is essentially 3 power/ground and 1 harness ground.


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I'll check it next time I see him. I tried his 7 to 4 connector as well and still nothing. Ironically, the 4pin worked with his truck and the 7pin connector worked with his boat trailer. :shrug: