Troubleshooting Trailer Wiring Running Light Fuse Blowing After 15 Minutes of Trailer Use

Published 11/19/2021

Products Featured in This Question

Hook Probe Circuit Tester

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Digital Multimeter with 42" Long Test Leads - LED Display

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Question:

I have a 2021 RAM and 2 different trailers. On my brand new 4 pin utility trailer, the running lights blow the 20amp fuse after about 15min. I tried a 25amp fuse and it worked for a good 30 min, then the lights started to flicker. Turned the lights off and on and they worked for about 5min and then the fuse blew. Could it be that the trailer is drawing to much amps for some reason? I tried the 4pin on the truck and a 7 to 4 pin, same issue! The other trailer 5pin works without a problem. Any idea? Thanks in advance.

asked by: THOMAS N

Expert Reply:

Since it is only happening on your new trailer we know that the problem is in the trailer wiring and not your 2021 Ram. What is odd is the time delay for the fuse to blow. Generally if there is a wiring short it will blow at random times and not after a certain amount of time.

What I think you have is a wire that is pinched on the trailer running light circuit. The pinched wire is likely causing the wire heat up and over time as it gets hotter it shorts to ground and causes your fuse to blow. That would explain why when you turned off the lights after they flickered they worked for another 5 minutes. I would refrain from using the running lights until you are able to get the wiring checked as this will generally lead to a fire.

You can use a Multimeter # PT89ZR to check the resistance in different sections of the wiring to help find any damaged portions of the wiring if it is not visibly evident on the wire that it is damaged.

expert reply by: Bud M