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Old Oct 14, 2020 | 08:35 AM
  #1  
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trailer running lights

all my lights work on my trailer with exception of running lights. did an electrical check at the truck side 7 pin and no power to running lights. Checked and replaced fuse 99 which was not blown but changed anyway. Not sure where to go next? 2017 6.7 Super duty lariat
 
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Old Oct 14, 2020 | 08:42 AM
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Are your headlights on? I'm sure that's a stupid question but...
 
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Old Oct 14, 2020 | 08:45 AM
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Get under the truck and pull the connection behind the 7-way plug. There is a common issue (might even have a TSB) with water intrusion there causing corrosion. Check for corrosion, clean it off, and replace the connector with plenty of electrical grease to help prevent it in the future.
 
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Old Oct 14, 2020 | 12:48 PM
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Funny, my 2017 Lariat F350 also lost the trailer running lights last time pulled. I will check the plug.
 
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Old Oct 14, 2020 | 04:24 PM
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Well... this thread is timely. I just got back home from a trip and noticed the running lights weren't working. Brakes, brake lights and directions worked fine but the running lights don't. I just ordered a 7-pin tester to confirm if it's the truck side or the trailer side. It sounds like I'm a couple days behind you with my findings.

Edit: Mine was caused by a blown fuse #99. Replaced the fuse and all is well. Hopefully you figure out what happened to yours!
 
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Old Dec 18, 2020 | 05:01 PM
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Same issue here. 2019 F350 Lariat SRW Tow package. Fuse 99 is not blown and no power to running lights. Any updates from the other posts on this thread?
 
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