I have an 89 F250 and my instructions for my trailer brake controller say not to tie into the brake light switch. I was just wondering which wire you guys tapped into for a controller.

 

I don't think I ever saw one that didn't tie to the brake light switch.. So, I am of no use to you on this, But I can and did bump it back to the top so maybe someone who does know can find it...

Just curious, what do the controller instructions say to tie to?

 

This is from the instructions

WARNING:
1989 - 1991 Ford Bronco, Econoline, FSuperduty,
and F150-350 Series:
• The red stoplight wire MUST splice into
the turn signal connector harness and NOT to the
stoplight switch.
• Connecting to the stoplight switch will break the
switch and result in no stoplights and no trailer
braking.

 

I would say to just splice it into the wire a few inches from the switch and be done with it!!

Be sure to splice into the out put side not the hot all the time side.

The switch moves with the pedal assembly, so that is probably why they say that.. If your wires were too tight and not move enough it MIGHT cause a problem... I really think it is a cover your butt move on their part......

YMMV

 

Thats kinda what i was going to try and if for some reason it didnt work i could just take the splice out. It just kinda threw me off since it was only the years of my body style

 

The reason they say you should splice at the turn signal switch connector IIRC had something to do with the RABS. I have my P3 controller triggered by the BOO switch on the pedal and I've put many thousands of miles on this setup hauling cars all over the country, never had issues with breaking nothing.

There is something to watch out for tho - because of the way these trucks are wired when the 4-ways are engaged voltage may backfeed from the brake lights to the BOO switch, I noticed that when my converter began to unlock and re-lock with the pulsing of the 4-ways while pulling uphill behind a loaded-down semi. My converter forced-unlock relay is wired in parallel with the brake controller on the output side of the BOO switch, so if the relay got triggered by the 4-ways then so would be the controller if I was pulling a trailer at the time. I plan on addressing the issue by installing a diode on the output side of the BOO switch after the brake controller and the converter interrupter relay, this should prevent voltage backfeed from the brake lights.

 

Thanks for the info, I will give it a try and see how it goes

 

Got it all figured out. My wiring kit actually had a diagram of what wire to use on the 87-91 f series and broncos.

 

Ok great, so what wire/circuit did they want it connected to?

I checked my controller, it said to connect it to the cold side of the brake switch (I used the adapter for plug and play to the connector under the dash, so I didn't have to get that involved for a change)

 

They tell you to use the light green wire from the main harness side of the connector. When you unplug the connection and look at the end of the plug, its the top, second wire from the left


Unfortunately, I didnt have the option of the truck being prewired for a controller.

 

They tell you to use the light green wire from the main harness side of the connector.

Yea same wire as found right at the brake light switch itself, however it would be after the RABS and cruise control is tapped into that circuit.