What a beautiful day in Indiana today! Anyway, I have a 78 F250 4x4 with cruise control that came with (when I bought it used) a hydraulic activated brake controller. I also have a 78 camper that I will be pulling with this fine truck! So, I'm checking out the lights and seven pin connector at the rear and find that the P.O. did an excellent job of wiring up the connector because all lights, TS, ect work with exception of the trailer brake! So, crawling under the dash and checking things out find that blue wire is connected correctly to the brake controller, but red power wire is disconnected. More investigation find that there is a red wire "hanging" near the brake switch connector. The brake switch connector has three wires going to it that look like they have never been messed with. So, after the book I just wrote, here is my question. What wires should I tap into? I don't have my tester with me right now, but I'll have it soon. All the other brake controllers that I have wired in have been through the brake switch, I just want to be sure that is the best way to do this on this truck..........

 

You'll have one wire going to the COLD side of the brake light switch(hot when pedal is pushed). One wire DIRECTLY to the battery (+)(put a 30amp auto reset circuit breaker at the battery) One wire to ground, preferably the battery (-). One wire from controller to trailer plug. Best bet is to use one of the newer digital controllers. They're more reliable. New controllers come with wiring diagrams to fit most vehicles.

This is the simplified version, and there are other things to consider. If you've messed with them before it'll be no problem. Just make sure you go straight to the battery(+) for power into the controller and not from the fuse panel. Makes life more enjoyable down the road.

 

I am sorry, but I have to disagree with shoot4fun. He said he has a hydraulic brake controller. If it is a true hydraulic unit, you need to tap into the brake system so it will actuate the rheostat lever. Then you tap one side of the rheostat to switched or switched (I like unswitched) power.

When you press on your brakes, you move the rheostat that picks up power from you power source and sends it to the brake magnets on your trailer. This unit has nothing to do with the brake lights.

JMHO!

 

Cruise control changes things for the brake lights system.The former Brake light switch becomes the Cruise shut down switch.
The actual Brake light switch is now attached to the brake pedal push rod of the booster

Aside from the Battery Power to Trailer and Trailer brakes applier wire. All the trailer lighting electrical should be spliced into harness at the back of the truck.

This changes when one has a new electrical brake controller.

Take a picture of this mess please.

SO there is no doubt what is going on.

Also, Is this a Kelsey Hayes controller?

The OP doesn't have enough info in it.

 

Absolutely! If it is a true hydraulic controller, pull it out and throw it away and get a good digital one! I did see the "hydraulic", but I assumed he was going to a newer style. My bad...

 

That is why we all have each others back bro. Unlike some, I will admit that I can and do make mistakes, and at my age, it seems to happen more frequently!

 

Great info - I'll take a picture of the mess and get back with you. Sorry for delay, just haven't been able to get at computer right away - I'll take pictures tonight and post tomorrow!