Troubleshooting Voltage Drop with New Electric Brake Assemblies on Trailer

Published 04/05/2019

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12 Gauge Wire - Black Primary - Per Foot

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Question:

Chris R. So 10.4 volts is an ample amount of voltage the run the units on my trailer and are you saying its best to ground all four units separately instead of tying them all into one main ground? Thanks

asked by: Josh

Helpful Expert Reply:

Some voltage drop off as power travels to each brake assembly on the trailer can be normal (within 1-2 volts of drop), especially if you have a longer trailer . If you are testing the brake output wires right before the assemblies themselves and getting 10.4 volts then this probably isn't an issue. Also make sure when you're testing for voltage that you have the brake controller set to max power and you're using the manual override (not stepping on the brake pedal).

Something else that could contribute to a loss of power is a weak or bad ground. I recommend going to each of the brake assemblies to make sure its ground wire is securely attached to a clean, bare metal surface that's free of any corrosion or debris. It's usually a good idea to even sand down the area on the trailer frame where you attach the ground wire to ensure a good connection.

If you are still having issues please let me know and we can continue to troubleshoot.

expert reply by: Chris R

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Joshua H.

4/5/2019

Chris R.

4/5/2019

Yes, if you're testing the voltage right before the assemblies themselves then 10.4 volts is acceptable and this is a relatively normal drop-off. There are still things you can do to improve the voltage if needed (if you actually notice weaker than ideal braking during travel) such as the ground connections as mentioned. Most people tend to just ground each wire individually to the trailer frame (see attached diagram) but you can certainly also tie them all into the main ground at the harness by the coupler. Typically with aluminum trailers this is the best route. You might also improve your voltage by going with a thicker gauge wire for the brake output circuit. We usually recommend no smaller than 12 gauge wire like # 12-1-1. If you are using a smaller gauge then I do recommend replacing it with something larger.

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