P3 Brake Controller Problem: "No Trailer" when it's all hooked up?
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From: Providence, RI
P3 Brake Controller Problem: "No Trailer" when it's all hooked up?
I'm finally getting a chance to use the P3 brake-controller, but it's not cooperating:
I've installed it in my '00 Excursion with the Ford adapter plug that I bought with the P3, and when I have the trailer hooked up, I still get the "No Trailer" warning from the P3.
The lights and blinkers work on the trailer, so I know that bumper plug is working, and the P3 is getting power, so I know at least SOME of the leads on that are working.
I installed the P3 on my old '97 F-250 ONCE (using the same adapter), and I recall it working then, but now, it doesn't recognize that the trailer is hooked up.
Which wire is it looking at to tell the trailer is hooked up, and what is it looking for that wire to tell it? Is there some fuse on my Excursion that needs to be in place for this P3 to not only power-up, but also recognize the trailer?
Any help troubleshooting this would be a great help, as I really don't want to miss out on my first weekend back to the trails in nearly a year...
I've installed it in my '00 Excursion with the Ford adapter plug that I bought with the P3, and when I have the trailer hooked up, I still get the "No Trailer" warning from the P3.
The lights and blinkers work on the trailer, so I know that bumper plug is working, and the P3 is getting power, so I know at least SOME of the leads on that are working.
I installed the P3 on my old '97 F-250 ONCE (using the same adapter), and I recall it working then, but now, it doesn't recognize that the trailer is hooked up.
Which wire is it looking at to tell the trailer is hooked up, and what is it looking for that wire to tell it? Is there some fuse on my Excursion that needs to be in place for this P3 to not only power-up, but also recognize the trailer?
Any help troubleshooting this would be a great help, as I really don't want to miss out on my first weekend back to the trails in nearly a year...
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Senior User
Joined: Nov 2003
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From: Providence, RI
There is a 30A fuse in that position, and there is no place in that distribution box for another relay.
The P3 has a nice diagnostic mode, which is showing voltage to the unit as well as brake-switch voltage when I press on the brake. A third wire on the connector to the brake-controller is the ground, so those three wires in the connector are working
It is just the output voltage and amps that is "0", which is the fourth wire on the connector, a blue one.
According to the factory instructions for the tow-harness (this was one of the things tucked into the rear panel when I bought the truck), the blue wire runs straight to the 7-pin plug at the hitch. All the other functions on the trailer work, so the rest of the harness is intact. I guess the next step will be to trace the continuity in that blue wire from the connector under the dash back to the hitch.
The P3 has a nice diagnostic mode, which is showing voltage to the unit as well as brake-switch voltage when I press on the brake. A third wire on the connector to the brake-controller is the ground, so those three wires in the connector are working
It is just the output voltage and amps that is "0", which is the fourth wire on the connector, a blue one.
According to the factory instructions for the tow-harness (this was one of the things tucked into the rear panel when I bought the truck), the blue wire runs straight to the 7-pin plug at the hitch. All the other functions on the trailer work, so the rest of the harness is intact. I guess the next step will be to trace the continuity in that blue wire from the connector under the dash back to the hitch.
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Bob, make sure you didn't lose your ground on the trailer. Those electric brakes are finicky about grounds....... One way I test them is to apply 12 volts at the # 2 connector on the trailer plug, which should also be a blue wire. You will hear the brakes engage if they are working properly. (I always have a spare battery laying around that I can set up by the trailer tongue for testing)...
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Senior User
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From: Providence, RI
Thanks!
Turns out it was a bad connection to the brakes on the trailer.
The Scotch-lock connections used for ALL junctions in the brake-lines on the trailer (
) were not making a good connection. I guess the P3 looks for a good signal from the brake-output to ground, and if it doesn't see that, gives a "No Trailer Connected" warning.
I replaced the Scotch-locks with crimped, soldered and shrink-wrapped connections, and all is well.
Turns out it was a bad connection to the brakes on the trailer.
The Scotch-lock connections used for ALL junctions in the brake-lines on the trailer (
) were not making a good connection. I guess the P3 looks for a good signal from the brake-output to ground, and if it doesn't see that, gives a "No Trailer Connected" warning.I replaced the Scotch-locks with crimped, soldered and shrink-wrapped connections, and all is well.
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