Trailer brake wiring on 1989 F-250 with ABS

[fatherdoug]

I just purchased a 1989 F-250 4WD with ABS. The vehicle came with a Drawtite Activator II brake controller already installed. I was checking the wiring and voltages at the plug at the rear of the truck, and I have a constant 12 volt signal coming from the blue wire(trailer brakes) without the brake lights on. After finding the wiring instructions on the good old internet, I discovered that the wiring connections on the truck were not correct.

The instructions say NOT to connect the red wire on the brake controller to the cold side of the brake pedal switch on 1989 - 1991 fords with ABS, but rather connect to the brake wire going to the multifunction switch.

My truck was wired to the cold side of the brake pedal switch. Can somebody tell me why the wiring is different on these vehicles with ABS? I am assuming the brake controller is fried inside because of the incorrect wiring?

I posted this question here because of the vehicle-specific directions for these fords. If the moderator feels it belongs in the trailer section, feel free to move the question to that section.

 

[95F350XL]

Umm there should be a factory harness under the dash. Use a test light and push the brake and see what wire gets hot when you push it, and hook it up and see how it goes. There is no factory harness under the dash? My 95 got 1.

 

[Fellro]

Many times they put some of those harnesses in, but you had to buy the part to finish them out. Some didn't even have it, they became popular some time around there. I know the 92 had some of the harness, but not all of it to make it work. I just had to figure out what wire did what and where they were to hook them up. Haven't looked at trailer wiring for the 88, it only has a Windsor, and we have 3 diesels to handle the trailers...

 

[subford]

I discovered that the wiring connections on the truck were not correct.

The instructions say NOT to connect the red wire on the brake controller to the cold side of the brake pedal switch on 1989 - 1991 fords with ABS, but rather connect to the brake wire going to the multifunction switch.

The blue wire being hot may be normal. Most brake controllers send power out on this wire to check the continuity of the brake circuit on the trailer to ground. They will also turn on an LED on the controler showing continuity.
The cold side of the the brake pedal switch is the same place as the brake wire going to the multifunction switch.
So it was wired correct.
I do not know why they said what they did in these instructions.

The instructions for it:
http://p.hostingprod.com/@drawtite.com/N5500.pdf

Your wiring diagrams:
http://i54.photobucket.com/albums/g91/subford/Brakes/090-01.jpg
http://i54.photobucket.com/albums/g91/subford/Brakes/042-01.jpg

/

 

[fatherdoug]

Thanks for the info. Subford, I have that same set of instructions. If you read the instructions, there are two different sets of instructions for the same application. It looks as if somebody did some half-arssed cut and paste when they made the publication. The instructions say to wire the controller BOTH ways on the same application.

As far as getting some voltage through the blue wire to the brakes, am I correct in assuming that voltage would normally be considerably less than 12 volts, if the blue wire is being used for a constant voltage source. I was thinking more like 4 - 5 volts. I am getting 12 volts to the blue wire.

I also looked up the instructions on the Hopkins website. It also says NOT to use the cold side of the brake pedal switch for the hookup. I am just trying to understand why the manufacturer says what they say?????

It looks like Ford didn't start adding a trailer harness until 1992 - 1994, depending on the application. I do know my 89 doesn't have one.

 

[subford]

As far as getting some voltage through the blue wire to the brakes, am I correct in assuming that voltage would normally be considerably less than 12 volts, if the blue wire is being used for a constant voltage source. I was thinking more like 4 - 5 volts. I am getting 12 volts to the blue wire.

I am not sure what voltage the unloaded blue wire would be when being tested with a DVM. I may go out and see what mine is a little later or check one on the bench. But I know my LED light is on when it is plugged into the dolly and off when unplugged.

Have you hooked it to a trailer or dolly to see if yours work or not?

 

[fatherdoug]

I did hook the truck up to the trailer, then raised one side of the trailer off the ground, and the trailer wheels would not turn. I did disconnect the brake controller and hook it up directly to the battery. After doing so, I also checked the voltage on the red wire which would normally go the brake wire. It is also showing 12 volts coming out of the controller. I think my controller is fried, but I would still like to verify HOW to hook up the new brake controller for an '89 Ford.

 

[subford]

OK I just bench tested a Drawtite Activator II brake controller on the bench.
Yes it has 12 VDC on the Blue wire but when I loaded that Blue wire with a resister it dropped to near zero volts.

 

[subford]

I think my controller is fried, but I would still like to verify HOW to hook up the new brake controller for an '89 Ford.

Did you look at the diagrams that I posted above for your truck?
The controller just needs to know when you put your foot on the brake so it should do its thing when the brake lights come on. If you have a hi brake light then you could hook it to that wire also. I do not know what the ABS has to do with it, that wire is at battery voltage all the way from the brake switch to the ABS module and the multifunction switch (same wire).

 

[fatherdoug]

Thank You, subford. So, my controller is better off in the round file?

 

[subford]

Thank You, subford. So, my controller is better off in the round file?

I would bench test it first and see if the blue wire goes very low when you load it.
The way it was wired would have nothing to do with it failing.

 

[fatherdoug]

Thanks for all your help, subford. I am gone for a couple of days. I will test the controller further next week.

 

[subford]

I also looked up the instructions on the Hopkins website. It also says NOT to use the cold side of the brake pedal switch for the hookup. I am just trying to understand why the manufacturer says what they say?????

Not sure why the started with 89 as I think 88 and before had the same brake setup. In 1992 the brake light wire was in a plug under the center of the dash and that is why they said 89-91.
The reason I think they said not to hook it to the cold wire on the brake light switch and I think this is the same on all FORD trucks in the 80's through 91+ is the brake light switch needs to be free to do its thing. If you hook a wire to it and I have seen this happen is the wire can and does hold the brake lights on all the time. I am not sure if this would stop the lights from coming on and the brake controller from working but it might.
In other words the brake light switch must be free to move and they wanted to stay away from that problem. They may have not worried about trucks 88 and older and where to hook the wire.

 

[fatherdoug]

I agree with you, subford. I ordered a new brake controller today. I already have the wiring ready to go, but I did rewire the red wire for the stoplight to the light green wire that goes to the multifunction switch, just to be sure. I think I will call drawtite tomorrow and ask why their directions are written the way they are. If I get an explanation, I will share it here.

Thank you for all the drawings and info. It is much appreciated.