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Testing Electric Trailer Brakes Using Direct Battery Power  

Question:

I have heard battery charger directly to the two wires on the electric brake and no humming in the brakes still don’t work what could be wrong

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Expert Reply:

You can indeed test a trailer's electric drum brakes by directly applying +12V power from a fully-charged battery.

You can apply this power to the hot contact on the trailer's plug (see photo please) or to an individual brake assembly's two wires. With a well-charged battery delivering power you should hear gentle humming from the brake magnets and feel resistance as you try to rotate the hub.

Please note that a battery CHARGER like # CTEK56353 cannot be used to do this test. You need a fully-charged 12V battery to do it. If you are using a fully-charged battery for testing and you have no response from the brake to this full battery power input then check the main ground wire on the trailer for a loose or corroded connection that is preventing power from reaching the brakes. You can also check each brake's ground wire. All ground must be made to clean bare metal.

You can also refer to the linked article for more on testing brakes.

expert reply by:
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Adam R
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Bruce profile picture

Bruce

7/30/2020

I tried to do this and when I touched the wires from the battery to the connector, one of them started to smoke. According to my new brake controller, there's a short somewhere. Could that cause the test wire to smoke?

JonG profile picture
Etrailer Expert

Jon G.

8/9/2020

Most definitely. A short somewhere can cause a multitude of problems. Find the short (broken/damaged wire, dirty connector, bad ground) and fix it then you should be good to go!
Tim profile picture

Tim

6/5/2024

Just to be clear we should apply positive +12v power to both the ground pin and the brake pin. No negative -12v ?

KevinC profile picture
Etrailer Expert

Kevin C.

6/5/2024

@Tim No, you'll only be applying 12v power to the brake output pin to power the magnet and activate the brakes. The ground is just labeled in the picture as well.
Tim profile picture

Tim

6/5/2024

@KevinC thank you. Because the second paragraph above says to both. That seemed very confusing to me.

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