Brake controller install help

[OldIron82]

Ok. I got a Tekonsha P3 brake controller and I have a discrepancy on where to install the "signal wire" to activate it. I have two of the same controller. One I bought a few years back that I never got installed in my 4700 International yet, and the other one I bought a few months ago to install in my 89 f350 dump. I had both boxes open just to see if there were any different mounting brackets and I noticed on the instructions one does not want you to splice into the stoplight switch circuit, citing a issue with ABS on the 89 through 91 E and F series. Instead, it wants you to hack into the turn signal wiring harness on the steering column. The older one with a revision date of '06 says use the turn signal harness, the newer one with a '14 revision date does not mention it and illustrates splicing into the stoplight switch circuit. Any thoughts on this? I would rather not touch the turn signal harness.

Also, is it absolutely necessary to hook directly to the battery as the instructions say? May I hook into a unused fuse location on the fuse panel and wire in a 20amp auto reset breaker as the instructions say? I like the fuse panel because certain ones are only hot with the key.

Thanks
OI82

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[hoodshauler]

Hook the power to the fuse panel like you stated would be fine IMO. I have never hooked to the turn signal circuit always just hooked to the brake.


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[ifrythings]

The only reason i can see why they want you to get the brake signal from the turn signal harness is that most shops use t-taps on the brake wire at the switch and the wire breaks off after awhile which will **** off the rabs and pcm, electrically both points are the same wire with nothing in between them.

Ford made a mistake on the 87-91 trucks with the turn signal switch, when you turn on your hazards it doesnt disconnect the brake switch from the brake lights, what this does is makes your brake controller turn on and off with the hazard on (also locks and unlocks the torque converter on autos). The only way to fix this is to put a diode between the brake switch and turn signal switch and add a 3rd brake light or resistor to the brake switch.

92 and later trucks solve this problem by disconnecting the brake wire from the brake lights when you turn the hazards on and they add the 3rd brake light to providing a constant load for the brake wire.

In the end just hook to the green wire at either the brake switch, steering column, rabs or cruise control and you'll be fine.

 

[OldIron82]

Oh damn! I remember a former employers truck had that problem. I had to pull over on the highway and as I slowed down I pulled on the 4-ways and tyre trailer locked up as the 4 ways blinked. Tell me more about this diode. Also, what is RABS? Thanks for the info thus far.

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[OldIron82]

*The* trailer. Not tyre.

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[ifrythings]

Rabs is Rear antilock brake system.

A diode is like a one way door for electricity, when you put in between the brake switch and turn signal switch it will prevent the hazard from backfeeding into the brake wire and causing that nasty effect that your former employee had. If you do put a diode in you have to put some kind of load onto the brake switch side so everything works correctly when the hazards are turned on, a resistor for led lights would work fine here or you could wire in a 3rd brake light.

 

[riotwarrior]

Do NOT Tie into fuse box....run seperate line w circut breaker directly from bat as instructed.

If u overload system could melt it down but a seperate line fused properly is much simpler to diagnose etc.

Dont rethink their instructions it is what they deem best.

JM7.3CW Eh!

 

[OldIron82]

Thank you for the info gentlemen. Over the winter when I have the proper time I would like to hook up the system with that diode. I'll ask for part numbers and more help at that time. Thanks again [emoji106]

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[OldIron82]

The only reason i can see why they want you to get the brake signal from the turn signal harness is that most shops use t-taps on the brake wire at the switch and the wire breaks off after awhile which will **** off the rabs and pcm, electrically both points are the same wire with nothing in between them.

Ford made a mistake on the 87-91 trucks with the turn signal switch, when you turn on your hazards it doesnt disconnect the brake switch from the brake lights, what this does is makes your brake controller turn on and off with the hazard on (also locks and unlocks the torque converter on autos). The only way to fix this is to put a diode between the brake switch and turn signal switch and add a 3rd brake light or resistor to the brake switch.

92 and later trucks solve this problem by disconnecting the brake wire from the brake lights when you turn the hazards on and they add the 3rd brake light to providing a constant load for the brake wire.

In the end just hook to the green wire at either the brake switch, steering column, rabs or cruise control and you'll be fine.

Pardon my ignorance but what are t-taps?


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[jwalterus]

Pardon my ignorance but what are t-taps?

Scotch-loks, vampire taps, pieces of junk.........

They are the worthless little SOBs that you put around a fully insulated wire and squeeze so they bite through the insulation, half break a good wire, and corrode a wire to the point you have to splice and solder in a few years..............

 

[chillman88]

Pardon my ignorance but what are t-taps?

These abhorrent little buggers...

https://www.lawsonproducts.com/laws...MI1MfFqaOz1QIVDqhpCh37JgP6EAQYASABEgLUQPD_BwE

 

[OldIron82]

*sigh* That's exactly what I used for tapping into the brake signal wire. Under the dash out of the elements I didn't think it would be a big deal. How can I do it properly?

The rear of my truck is riddled with them from the previous owner and unfortunately that's how its going to stay until winter when I have time to solder the connections properly.

 

[79jasper]

How can I do it properly?

solder the connections properly.

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[OldIron82]

Hooking two wires together butt to butt I have done plenty of times. But how do I add a wire to a existing wire? Strip the insulation, solder to it then electrical tape it? Is there a "add a circuit" connection I can solder in?

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[79jasper]

Commonly called a y-splice.
I'll strip a section of the current wire, add the joining wore, solder, electric tap, small zip tie to keep the tape from coming off.
There's some self sealing electric tape too.


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