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RESOLVED: Running lights not working - help diagnosing?

HelotesAg

Active member
With the days getting shorter, I drove after dark for the first time in a while on Friday and I noticed that I had no running lights. The brake lights and turn signals worked though. Has anyone experienced this and or have any ideas on how to troubleshoot it and figure out what's wrong? I'm going to have my son bring his truck over and plug it into his truck to see if they work or not to eliminate my truck as the problem. After that I'm not sure where to look.
 

Jim Beletti

Owner Experience Liaison
Staff member
Hi @HelotesAg - I have a suggestion for you.

With the 7-wire cord connected to the truck, truck running and headlights on, remove the cover of the 7-wire junction box and using a multimeter set to DC volts, check for 12 volts on the sides of the screws /posts between white and brown wires. See image below. If you have good DC power there, then you know the truck is sending it and the trouble is further downline on the RV.

I'm also providing a link to our online resource on the 7-Wire cord and how we use it on our brands at Alliance - LINK
Screen Shot 2022-11-20 at 2.04.54 PM.png
 

Grassjohn

Well-known member
A quick check - on the trailer 7-wire connector, use a piece of wire to connect the top two terminals (near the “notch”) to apply +12 volts to the running lights. This way you’ll know if the trailer wiring is okay.

Terminals TM3 to AX4 in the attachment.

Do not do this to the truck…
 

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HelotesAg

Active member
A quick check - on the trailer 7-wire connector, use a piece of wire to connect the top two terminals (near the “notch”) to apply +12 volts to the running lights. This way you’ll know if the trailer wiring is okay.

Terminals TM3 to AX4 in the attachment.

Do not do this to the truck…
Thanks Grasjohn - your test helped - When I connected them I got lights on the trailer. I noticed that the connectors on the plug were pretty far apart so I squeezed the blades closer and plugged it into the truck and it worked! Thanks again!!
 

Jim Beletti

Owner Experience Liaison
Staff member
Thanks Grasjohn - your test helped - When I connected them I got lights on the trailer. I noticed that the connectors on the plug were pretty far apart so I squeezed the blades closer and plugged it into the truck and it worked! Thanks again!!
Happy to hear you found and corrected the issue. Thanks for using the forum to seek a solution and for circling back with the fix.
 
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