Trailer Brake Issues

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jforrest

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I have a 2018 Ram 3500 dually and a 2007 3500 single axle. When connecting to a trailer with the 2018, all the lights, etc. work but the brakes lock up and I can't tow. Now I hook up the 2007, everything works normal. I have 4 trailers and the scenario is the same. I check all the wiring, installed new breakaway switch and still the same issues. Took the truck to the Dodge Dealer, found nothing. Next, I started pulling fuses. When I pull F30 fuse, trailer tow receptacle, all works normal, I can tow my trailers without issue. Can this be explained? And exactly what does the trailer tow receptacle do?
 

JPT

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When you pull the F30 fuse, do you actually have brakes? Or is it that everything works but the brakes?

Do you get the charging light on your break away brake battery box?
 

crash68

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As stated above, the F30 fuse is the constant 12V that is commonly used to recharge the break away battery for the trailer brakes and provide 12V to the trailer. The F11 is the fuse for the actual trailer brakes that goes through the ITBM
You might want to check the voltage at the truck side and the wiring on the trailers.
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jforrest

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Yes. With the F-30 fuse in place, the light on the breakaway switch is on. Pull the fuse and it's off. I do have brakes on the trailer when the fuse is out. If I pull the pin on the brake away switch, the light on the switch come on as it normally would. Not sure if the battery is being charged on the trailer with the fuse out. I'll recheck the wiring at the trailer plug, just odd that it happens on all trailers and my 2007 ran work just fine when plugged in.
 

crash68

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definitely sounds strange, only thing I can think of is to check for continuity between the #2 & #4 pins(see pic). The only time that should happen is when the break away switch is pulled on the trailer side, and nothing on the truck side(F30 pulled).

If you plug the trailer in while the truck is running and then unplug it(truck still running), does the truck show the trailer disconnected icon on the dash?
 
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jforrest

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With the F30 fuse in, there is continuity between #2 and #4, when pulled, No. When the fuse is in, the truck doesn't recognize the trailer, even though all the lights, turn signals, brake lights work. When the fuse is pulled, the truck recognizes the trailer and all the lights work.
 

crash68

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what about on the trailer side? You would have to pull a battery terminal, but the trailer brake and +12V shouldn't see any continuity unless the brake away switch is pulled. When you say the truck recognizes the trailer with the fuse pulled, makes me think something is shorted or spliced in the wrong spot... If you weren't in Idaho, I'd come drink your beer...lol and help figure this one out.
I don't think any of the turn, running or brake lights are involved in the issue.
 
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jforrest

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Thanks. I’ll keep looking. Headed south for a few weeks. I’ll have a cold for you.
 

BossHogg

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just odd that it happens on all trailers and my 2007 ran work just fine when plugged in.

Question, does your 2007 have battery power on the number 4 pin? I have three trailers with electric brakes I pull with my 2015 without the issues you describe. This sure sounds like a common wiring issue with the break-away power.
 
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