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Trouble Shooting Tekonsha AccuTrac Brake Controller Not Recognizing Trailer on a 1999 Ford F-150


Green light on controller does not illuminate. Ive checked the brake controller to the plug per the Tekonsha troubleshooting guide the green light illuminates when the test light is grounded and the blue wire/spade is touched. There is continuity between the trailer plug ground spade and the trailer when checking resistance between blue and white spades on the trailer plug, the resistance is 1. Where is a good place to start troubleshooting the blue wire? A breakaway system is installed on the trailer previous owner states all electrical systems worked on his 2005 F-250. I have a 1999 F-150.


Expert Reply:

I spoke with my co-worker, Bob, about this for some time this morning. We are both thinking you have a ground issue somewhere or possibly a short. Between the trailer brakes and the brake controller there are several grounds that need to be checked. I will start at the top and work down one by one till we can find the source of the problem. Some of this may be redundant so bear with me.

I assume you mean that the green light does not come on when the truck is on and the trailer is connected. This means that the brake controller is not seeing that the trailer is there. This can mean there is a something wrong with the brake controller, the trailer or both. So the first thing to do is try to eliminate one side.

Turn on the truck, and with someone in the vehicle, touch one end of a circuit tester to the ground pin, 7:00 position, on the 7-Way at the rear of the truck. Touch the other end of the circuit tester to the brake controller pin, 5:00 position. At this point the green light should come on indicating that a trailer is connected. Have the person in the truck press the brake pedal, and activate the brake controller causing your circuit tester to light up or beep. If everything works, then we know the problem is on the trailer. If it does not work as described above, then you need to check the ground wire on the 7-Way.

I imagine the truck will check out fine, so the next step would be to check the trailer. Check the ground wire for the trailer connector. Make sure the connections are clean, sturdy, and the wire is not frayed. Check the trailer brake magnets. They will have two wires coming off of them, one connected to the trailer frame for a ground, the other connected to the brake controller wire. Make sure these connections are solid, clean and not loose. Trace the brake controller wire back up the trailer frame and check for nicks or frays in the wire.

The brake magnets may also be shorting if they have worn beyond their usable life. If you look at the magnets and you see the copper windings the magnets are shot. They may also have a short in them. Take an ohmmeter and touch one end to one of the magnet wires and the other to the other magnet wire, with the trailer disconnected. If your brakes are 7 inches then your you should see 3.8-4.0 ohms, if you have 10-12 inch brakes, then you should see 3.2-3.5 ohms.

If none of this helps, please write back and we can see what the next steps are. If you find the problem and get it corrected, please write back and let us know.

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