Breakaway switch and brake lights

bearwayne wrote:
Yesterday, I replaced the cable that connects the 5th wheel to the 7 pin connector on the truck. Luckily, the cable I ordered used the same color scheme as the existing cable (I tested old and new cable with a multimeter) and after connecting everything, the tail lights, turn signals, brake lights and running lights all worked as they should.

Then I decided to test the breakaway switch. I could not tell that anything happened when I pulled the pin. I checked the wire from the breakaway switch and I had voltage. Today, I tested it again after filing the contacts in the breakaway switch with a nail file. Again I had voltage (I think it was 12.5V), but the brake lights don't come on and I don't hear the brakes humming. I reattached the cable to the tow vehicle, and I can hear the brakes humming when the brake pedal is pressed as well as when the manual switch is pressed on the brake controller.

Shouldn't the tail lights come on when the breakaway switch is tested? I suspect that not enough current is passing through the breakaway switch to activate the brakes and the brake lights (I don't have an ammeter to test it.) I have already ordered a new one from Amazon.

No, the brake lights are not wired to the breakaway switch..

No you will not hear any "humming" at the brakes, the break away switch sends pure 12V DC to the magnets.. There is no way pure DC will "hum" in any way shape or form..

You can check to make sure your brakes are working when the break away switch is activated by using a compass, by jacking up the wheels and trying to turn them by hand.. or my favorite way, use your vehicle (with the trailer to vehicle cable disconnected) and see if the brakes slide the tires..