Identifying Small Black Box on Side of Trailer with Small Battery Inside

Published 04/09/2020

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Question:

I wonder if someone can help me identify the proper name Is box with small battery and a small green board and a device like car alarm fob? Is burned and over heat , my trailer lights won’t work but brakes works

asked by: Eduardo M

Expert Reply:

What you sent in a picture of looks like the breakaway battery on your trailer. This is used to activate the brakes on your trailer if you're trailer were to ever become uncoupled. While we do have replacement batteries available, since it looks like the internal components got melted I recommend just replacing the entire thing with the Hopkins # 20099 which is compatible with single and tandem axle trailers. I have attached an installation video that you can reference.

Your lights not working is an entirely different issue as the breakaway kit should only be connected to your trailer brake circuit. For your lights you want to test your vehicle 7-Way with a circuit tester # PTW2979 to make sure all the functions are existing (see attached photo). If your vehicle 7-Way doesn't have those functions (and they previously worked) then you likely have some fuses that need to be replaced. You can find which exact ones by looking in your vehicle owner's manual.

If you do see those functions on the vehicle 7-Way then you have some wiring issues on your trailer and you need to check every from the 7-Way plug all the way to your lights. Make sure all your grounds are secure and corrosion-free, and check to make sure none of your wiring is damaged.

I have attached some helpful articles on wiring that you can reference as well.

expert reply by: Jon G