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Tekonsha P3 install, late model Ford

Tour1
Explorer
Explorer
I bought a Tekonsha P3 Electronic Brake Control for my Ford E350 van. The instructions contain a warning sheet that says on some vehicles when the manual control is used the stop light switch can ground the circuit and destroy the unit. I tested the circuit with a high impedence multimeter and brake switch not activated. The readings were 1.9 ohms with ignition off and 2.9 ohms running. The wiring diagram for this van says the brake pedal switch also directly powers the high mount (3rd) stop light while signaling the Powertrain Control Module (PCM) and the Smart Junction Box (SJB). Supply to the pedal switch is Hot At All Times fused 10 amps.
So will the unit be destroyed if I activate the Manual control with the ""red" wire connected directly to the Brake Pedal Switch? If so, can I install a diode or diodes to prevent "Manual" activation current from trying to power the 3rd stop light circuit?
Is there another suggested source for the brake pedal signal or if a diode won't work, can I put in a relay to isolate the Tekonsha brake switch signal when the brake pedal switch is not activated?

The above is a direct quote of a question I asked via the Contact Tekonsha website, I'm repeating it here because it's a Saturday night and I don't know if they answer that kind of question for DIY people. I'm wondering if any of you know the answer, or if you are sure I don't have to worry about it. The warning sheet has a work-around for 1998-2005 models that hints maybe 2006 & up are fine as-is. The copyright on the sheet is 2011. I'm thinking a single LED light might not kill the P3 but an array of HIDs would be as good as a short to ground.
7 REPLIES 7

Tour1
Explorer
Explorer
Tekonsha got back to me and said basically the current used by the 3rd brake light etc was not a problem, so an install on the 2013 without an isolating relay should work perfectly. I already wired up and installed the relay so I expect to keep it, leaving well enough alone.
I need to find an alternative to google photos, even I can't see them unless I sign in. When I do I'll make my pics easier to see.

MEXICOWANDERER
Explorer
Explorer
Try the telephone ๐Ÿ™‚

Better than emptying a fire extinguisher.

Tour1
Explorer
Explorer
lawrosa wrote:
Watch this video...



https://www.youtube.com/watch?v=741QNSqxPCw

That's the one that takes me an hour per minute of video.
They don't demo the unit but I hope it works. Also there may be differences between an E350 and a lighter van. Just in case, I came up with a proposed wiring scheme and I'll try it if I don't hear confident words or alternative fixes from Tekonsha. I am on a PC that doesn't get the e-mail I gave them so I can't check if they answered me right now.
Images don't work for me but here's a link that might:
https://goo.gl/photos/xDgCNj29UA3cyLva9

lawrosa
Explorer
Explorer
Watch this video...



https://www.youtube.com/watch?v=741QNSqxPCw
Mike L ... N.J.

2006 Silverado ext cab long bed. 3:42 rear. LM7 5.3 motor. 300 hp 350 ft lbs torgue @ 4000 rpms
2018 coachmen Catalina sbx 261bh

Tour1
Explorer
Explorer
It's a 2013 with the canbus module system. It doesn't have the factory 7-pin setup. I bought the adapter to connect the P3 to the standard harness. I also have the 4-pin flat connector (installed & functional) to 7 pin connector, with a 2-wire cable heading up front for power & brake. Other than the red wire (vio/wht on the Ford side) everything is like a you-tube I watched.
Except a minute of you-tube done takes me an hour to do, longer if I have to add more parts.

time2roll
Nomad
Nomad
Not an issue if you use the much easier harness for plug and play.

Did you buy a harness or are you wiring this manually?
My instructions say to use the light green wire not the red wire from the brake light.

What year is the van?

lawrosa
Explorer
Explorer
what year van? Should just be a ford adapter plug. Ive never heard of what you describe..
Mike L ... N.J.

2006 Silverado ext cab long bed. 3:42 rear. LM7 5.3 motor. 300 hp 350 ft lbs torgue @ 4000 rpms
2018 coachmen Catalina sbx 261bh