Troubleshooting Interior Lights on Trailer Not Working When Connected to Tow Vehicle

Question:

I have a Lark 5’X8’ enclosed trailer with the interior light wired to the running lights. When connected to the tow vehicle all exterior lights work fine but the interior light doesn’t work. When troubleshooting with a 12v battery at the 4 pin flat plug it works fine. My tow vehicle is a 2010 Escalade that has also been used to tow multiple trailers with no exterior light issues. Thanks

asked by: Dennis

Expert Reply:

It's possible that the interior lights on your Lark enclosed trailer are simply exceeding the amperage capacity of the running light circuit on your Escalade. I recommend first verifying the amperage draw needed for the trailer's interior lights to see if this might be the issue.

Otherwise it is just a matter of checking the connection from the interior lights to your running lights circuit. Since you know the 4-Way wiring on the trailer is good after testing it with 12V power, you will want to turn your attention to the vehicle. You can test the running light circuit on your Escalade's 4-Way with a circuit tester like # PTW2993 to make sure it is getting power with the running lights activated. If not, you will want to check for any blown or missing fuses related to trailer running lights, replacing as needed.

Please let me know if this does not resolve the issue and we can continue to troubleshoot

expert reply by: Chris R