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Old 11-07-2013, 02:44 PM
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topper/3rd brake light wiring

I think I have about twenty hours into this project. I installed a topper on my 01 f350 last weekend. I wanted to wire the brake light into the 7 pin fifth wheel plug in the bed of my truck so I didn't have to cut and splice into any wiring. I can't seem to get the brake light to work unless I draw power from the 12v auxiliary from the plug. Am I missing something or is it just not going to work? I was reading on another forum that this can't be done because the power to the plug isn't enough to power an additional light...... this don't make sense because I can power the brake lights on my fifth wheel and boat with no issues just not the brake light on my topper. any suggestions?

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Old 11-07-2013, 03:42 PM
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This shouldn't be an issue... are you checking power with a test light while someone is depressing the brake pedal? if you get power via the testlight at the pin it should all work... if you have the correct pin... now if it is not enough of a power source which like you said shouldn't be the case you can use it to trigger a relay... use a 4 or 5 pin relay with pin 30 to the brake lights, pin 87 to the battery, pin 86 to the brake light pin in the plug, and pin 85 to a chassis ground... this will allow the light to pull power from the battery to illuminate the light and the plug to only charge the relay to turn on and off... but i'm guessing you have an issue in the plug have you checked the fuse for the brake light circuit in the plug? or hooked up a trailer to it to verify it's still working properly? also have you checked what you're grounding the topper light to it might not be making ground... hope some of these tips help
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Old 11-07-2013, 03:47 PM
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You should be able to get it to work by connecting it to either of the signal contacts. You are connecting the ground, right?

edit....Sorry I am wrong, if connected to the signals, it would flash when that signal is on.......needs to go up front before the flasher I guess
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Old 11-07-2013, 04:09 PM
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I think I might have found more issues. I plugged my fifth wheel into my truck to find the only thing I had was running lights. I don't understand because everything worked fine a month ago. I'm into more digging now I guess. Will all the lights work on the fifth wheel if it's not actually hitched to the truck? just wondering if that's how the trailer gets its ground?
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Old 11-07-2013, 04:44 PM
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There should be a white wire, which is the ground, #1 pin on the 7 wire plug. It's been my experience that actually hooking the hitch is a better ground and I have used jumper cables on the ball of the truck and a bare spot on the trailer frame, works well.
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Old 11-07-2013, 05:59 PM
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center-high-mounted

The center-high-mounted brake light will only work when it's NOT controlled through the turn signal switch.
It must be controlled directly by the brake light switch. Connect to the brake light switch wire before it goes into the turn signal switch.

vicrod
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Old 11-07-2013, 06:38 PM
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Quote:
Originally Posted by vicrod View Post
The center-high-mounted brake light will only work when it's NOT controlled through the turn signal switch.
It must be controlled directly by the brake light switch. Connect to the brake light switch wire before it goes into the turn signal switch.

vicrod
so can it be installed using the 7 prong trailer plug?
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Old 11-07-2013, 07:00 PM
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hi,
did you look for a light green wire in the harness to the rear? might even be a blunt/pigtail lead. ford typically leaves a wire for the CHMSL (center high mount stop light) on their pickup models.
mark
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Old 11-07-2013, 08:26 PM
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I will look I'm my Haynes Manuel to see if I can find the wire on the diagram.
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Old 11-08-2013, 03:34 AM
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There shouldn't be any reason you couldn't use the 7 wire trailer plug..... it doesn't know if it's lighting a trailer brake light or a topper brake light. make use you use #1-white wire for the ground.
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Old 11-08-2013, 05:35 AM
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so would I draw power from the left or right turn signal prong or the brake controller prong?
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Old 11-08-2013, 08:00 AM
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You can use the 7 wire plug, but unless you have a brake controller fully operational and trying to activate the trailer brakes, there won't be any voltage on the brake control pin at the back. The controller in the cab acts like a relay to apply voltage to the brake control pin at the trailer plug to activate the brakes. It is not directly connected to the brake light switch. Some controllers are based on time and others have inertial switches.

I think it would be just as easy to locate the wire running to the high mount brake light and use that with a relay to turn on the light on the topper. You may have to splice into one of the light wires, but you could use one of the cheap wire-taps to make the connection. The actual power for the topper light would be run through the relay directly to 12 volts, so the wire-tap would have very minimal current through it.

Bruce
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Old 11-08-2013, 08:47 AM
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so I crawled under the truck this morning and I'm about 2 seconds I found a wire with a big label on it that says " center high mount stop lamp". lol, I think I'll just run this wire to the center of the 7 prong plug to power the light. then I can use the 12v aux for the dome light and also get ground from the plug that way it will be plug and play for easy installation and removal. I'll let y'all know how it works out.
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Old 11-08-2013, 03:27 PM
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Is your center pin not wired up? Should be for rev lights........now I don't know many trailers that have rev lights lol
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Old 11-08-2013, 08:12 PM
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it was wired for reverse lights, but now it's weird for a fourth brake light
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