Tracing Intermittent Short In Trailer Braking System

Question

Question:

I bought the Tekonsha P3 controller from etrailer and have installed it in my 2010 Tundra. The control indicated a short. I checked the ohms at each brake and they read in specks at 3.7 to 4 ohms. I hooked up the trailer and let it move forward at fast idle and applied the electric brakes. The first three times all seemed to operate normal and stop the truck using the trailer brakes only. On the forth time the P3 indicates a short and the brakes do not work. I disconnected the trailer plug and read the ohms across the plug ground and the electric brake connector. The meter indicates 2 ohms. Which by most standards 2 ohms would be a short. When you wire two 4 ohms in parallel and read across them wont the reading be correct at 2 ohms?

asked by: Stacy W

0

Expert Reply:

It sounds like you have an intermittent short somewhere in your braking system. The readings you are seeing are correct, because the short is intermittent.

An intermittent problem can be very difficult to find, but your best bet is to physically examine the brake circuit on your trailer, from the connector all the way to the brake magnets. Look for a pinched wire, or cracked or worn wire insulation that would allow the copper conductor to intermittently contact the trailer frame and create a short. You will also need to pull the hubs to examine the brake magnet wiring inside the brake assembly, once again looking for cracked or worn wire insulation. If your brake magnets are becoming worn, you might begin to see an intermittent short. If you examine the front face of your brake magnets that ride against the inside of your brake drums, and see any of the copper wiring from the interior of the magnet, the magnet is worn to the point that it needs replacing.

expert reply by: Mike L

0

Answer 1

You said you checked the brake magnets. When inspecting them did you notice if the windings inside the magnets are showing? If so this is most likely the reason that the short is showing up on the controller when the vehicle is moving. This would…

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Answer 2

You should have continuity between the 5 o'clock brake output pin and 7 o'clock ground pin in your 7-way connector with the brakes applied. I recommend turning the trailer brake controller to its max setting and having someone apply…

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Answer 3

The Advent AC unit part #ACDOM150 will work great as a replacement for a Dometic Duo Therm unit like you have. We had a customer come back and tell us how well this worked as a replacement for a Duo Therm and that no modifications were needed.

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Answer 4

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Answer 5

When there is bizarre trailer brake behavior the first place to check is the trailer connectors for corrosion. Check out the trailer connector on your tow vehicle for corrosion and clean as necessary. Electric trailer brakes aren't really…

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Answer 6

Yes, when your brake controller is sending power back to your 7-Way connector you should have continuity with a Multimeter #PT89ZR between that and the ground pin. To ensure that you are sending power back to the brake controller pin set your brake…

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Answer 7

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Answer 8

It sounds like you are speaking of the wires for the brake magnets. If this is correct, you will need to connect one of the wires to the brake controller output wire on your trailer connector and the other wire will need to be grounded to a clean…

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Answer 9

Did you for sure run the white wire to the negative post and the black wire to the positive post? It sounds like you may have ran them backwards based on the arcing you mentioned. If you have verified the correct wires to the correct posts you most…

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Answer 10

You can definetly check the resistance of your trailer brake magnets. Depending on the trailer brake size you have, you are looking for a specifc range of Ohms. If you have 10 or 12 inch brakes you should see 3.0-3.8 Ohms, and if you have 7 inch…

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Answer 11

For your 2018 Chevy Express 2500 the Prodigy P3 brake controller #90195 is a really great choice. To install it in your van that does not have any trailer wiring currently does require you to start with a 4-way #118392 which installs easily. I…

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Answer 12

If applying the manual over-ride lever on your Hopkins trailer brake controller, such as the Agility #HM47295, sends brake power back to your Tundra's 7-way then you know the circuit is functioning. You can test by having a helper press the lever…

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