ELECTRIC BRAKE ?

If it’s grounded through the hitch, fix that problem before looking further. Should be grounded via the white wire in the connector. The ball is not a satisfactory ground.

Good excuse to buy a new tool :)

Get the DC clamp-on ammeter and look for 3 amps per wheel. This checks the coil, wiring, connections, controller output all in one swoop.

Otherwise I would pull and inspect at least one drum.

Magnet testing

In this article, look at the ohms, you likely don't have a DC AMP meter. You can test at the trailer plug for a ballpark figure, just check from the brake pin to ground. Multiply the reading by four if you have four brakes. The result should be 3.0 to 3.8 ohms. If you are considerably out of tolerance, start disconnecting wires at the brakes and check.

A brake magnet can go out like a light.

Hi guys. I am considering your advice regarding wiring. Trailer is grounded through hitch, load bars and plug and has worked well for 19 years. Still could be a ground issue. When magnets go out is it an all or nothing?

Bob,

While you are doing the above checks, make sure that you have a good and solid ground connection between the TV and TT. That is a well known source of problems. Don't just count on the 7 wire plug to get this right. I have often found that the ground to the trailer is not all that well thought out and good. The result is problems forever.

Matt

My guess is wiring. Start at the tongue and trace the wiring down to each brake. Redo any connection you find. Look for wire insulation rubbed through where the wires enter and exit the axle tubes.

Best bet is to run all new wires minimum 12 gauge, 1 wire per brake on the outside of the axle tubes. Join all 4 brake wires (2 wires for a single axle trailer) into a junction box near the tongue. Then join the brake wire from the tongue to the 4 brake wires in the junction box.

Make sure you have a ground wire from the trailer to the tow vehicle. Don't rely on the trailer ball for the ground.

Now test drive.