Electric Brakes Troubleshooting

[jpich0001]

I had a previous thread regarding "Inline fuse from battery to converter overheating / blowing" where I was advised to check my brakes because I pulled the breakaway pin for an extended period of time. I have gotten to checking them and this is what I'm seeing with the first one:

Connected the trailer to my truck and checked the amperage to the wires when pushing the brakes. I got 0.3A to the black wires and 0.9A to the white/blue wires (See picture). The Dexter manual says you should see 3A per magnet.

When I push the breaks on my truck, the magnets are, in fact, working as you can see in the picture. They seem to change in strength each time. Sometimes it's strong enough where I can't pull the plyers off and sometimes they fall off on their own. I have no experience with this. Is it because of the low current? Is this a sign of damage to the magnets?

[ARoamer]

I fail to see how you can blow a fuse from your battery to converter, are you towing it plugged in to a 120VAC source?

My current TV does not supply full amps unless gain is set to max and brakes are applied hard. Old style aftermarket controllers were generally on or off, gain sets amps. Depending on your TV and how you apply brakes you will likely see different amp readings.

How are you checking amps for breakaway system?
Disconnect trailer from TV and 120VAC. Don't test while connected to anything, 12V backfed into your brake controller may not make it happy...
Connect amp meter between battery and breakaway switch.
Pull breakaway switch.
On each individual electric brake magnet the amperage draw would be 3.0 to 3.2 max amps at 12 to 13 volts on 7-inch brake magnets and 3.2 to 4.0 max amps at 12 to 13 volts on 10 and 12-inch brake magnets.
Per regs the breakaway system should be able to work for 15 min., don't leave it on.

[DocBrown]

You need new magnets. The one in the photo is worn through. That's why the magnet strength isn't consistent. My dad had the same issue. I put new magnets on for him and the brakes work great now.

[jpich0001]

Originally Posted by ARoamer

I fail to see how you can blow a fuse from your battery to converter, are you towing it plugged in to a 120VAC source?

My current TV does not supply full amps unless gain is set to max and brakes are applied hard. Old style aftermarket controllers were generally on or off, gain sets amps. Depending on your TV and how you apply brakes you will likely see different amp readings.

How are you checking amps for breakaway system?
Disconnect trailer from TV and 120VAC. Don't test while connected to anything, 12V backfed into your brake controller may not make it happy...
Connect amp meter between battery and breakaway switch.
Pull breakaway switch.
On each individual electric brake magnet the amperage draw would be 3.0 to 3.2 max amps at 12 to 13 volts on 7-inch brake magnets and 3.2 to 4.0 max amps at 12 to 13 volts on 10 and 12-inch brake magnets.
Per regs the breakaway system should be able to work for 15 min., don't leave it on.

I had pulled the pin during camping as a backup brake to ensure it wouldn't budge. Battery quickly died and I plugged in shore power to recharge it which led to fuses blowing and/or melting. I know not to ever do this again and the reasons why.

With only the 12V battery connected, (no TV and no shore power) I used a clamp on ammeter to check amps for breakaway system. Each wheel was receiving about 3A when pin was pulled.

[jpich0001]

Originally Posted by DocBrown

You need new magnets. The one in the photo is worn through. That's why the magnet strength isn't consistent. My dad had the same issue. I put new magnets on for him and the brakes work great now.

Thanks, that's what I was thinking but didn't know if it was just the magnets or something bigger. Just ordered a new set.