Trailer brake wiring issue

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Jun 19, 2012 | 06:58 PM

Midnite1987

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From: Edmonton AB, Canada

Trailer brake wiring issue

I have the factory tow package and I just replaced my brake controller because I thought the old one wasn't working. Well the controller lights up when the brake is pressed like it should but I get nothing to the back end of the truck. And the 12v constant at the plug doesn't work either. Every other function at the plug works except the trailer brakes and the12v constant.

I have checked all the fuses under hood and in dash, all hood
I checked at the plug under the dash for the controller and I'm getting the correct output into the harness.

Is There something between the plug and the controller and the plug and 12v ?? A relay that controlls it? I dunno

Jun 19, 2012 | 07:10 PM

White 97 xlt

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From: Cleveland, TN

I'm not sure about the brakes, but the as you say "constant" power is controlled by a relay, and there is power ONLY when the key switch is in the run position..

Jun 19, 2012 | 07:39 PM

RV_Tech

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From: Bristol, TN.

Quote:

Originally Posted by White 97 xlt

I'm not sure about the brakes, but the as you say "constant" power is controlled by a relay, and there is power ONLY when the key switch is in the run position..

Your 12 VDC+ should be hot when the ignition is on.

The issue with the brakes is most likely in the seven pin at the rear of the truck. What controller are you using and are you testing the controller using the manual override (or with the brake pedal which will not work with anything except timed controllers).

Steve

Jun 19, 2012 | 08:30 PM

Midnite1987

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From: Edmonton AB, Canada

I tested using the manual override as well as the brake pedal. Both ways testing the output of the controller with test light it gradually got brighter the farther I presse the lever or the pedal. I have a Reese brake controller. So it could just be that the relay is bad for the 12v then? Ill take a look at the relays and swap a couple around if I can and see if that's the issue

Jun 19, 2012 | 08:53 PM

RV_Tech

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From: Bristol, TN.

Quote:

Originally Posted by Midnite1987

With an controller with an accelerometer, the output to the trailer brakes matches the rate of deacceleration of the truck. While you may get a weak voltage to the seven pin using the brake pedal, the full output is only available via the manual override. With a timed controller the output ramps up the longer the brake pedal is depressed, so the braking action of the trailer is more jerky.

Brake controllers themselves almost never fail. I have to deal with maybe one bad controller a year. The liability issue is so great manufacturers test the crap out of them.

While there is a possibility you have a bad relay, do not overlook the alternative of a pin that is corroded or rusted in the seven pin, which is the thing with the greatest probability. Take your time with this as I am betting it will turn out to be something very simple.

Good luck,

Steve

Jun 19, 2012 | 09:07 PM

Midnite1987

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From: Edmonton AB, Canada

I'll also pull the plug apart tomorrow and see if anything Is coroded in The back.

Since the fuse isnt blown for the 12v trailer wire that would tell me that it's not grounded anywhere.

Jun 20, 2012 | 05:33 PM

redmondjp

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From: Redmond, WA USA

I don't know what year your truck is, but on my 1990, there is a 20-gauge fusible link right next to the battery that powers the trailer wiring (and it burnt open on my truck - which also takes out power to the underhood light). You might check for that on your truck as well.