Have an interesting issue on a truck I am wiring up for a trailer.

The truck is 24V. The controller is a 24V-12V controller of a cheaper variety as the truck is of off highway use only.

I also have fitted a 24-12V converter to go to the reverse light pin to act as an auxillary 12V supply to charge the breakaway battery and also charge a battery on the trailer that powers the hydraulic tipper.

Both wires are 6mm in the same sheath and run from the cab to the rear of the truck (about 4m). Upon testing it magic smoke was released from the 24-12V converter. A power diode burnt up. Replaced it and all is fine.

Isolating and testing the wire that goes from converter to rear finds that when the brake is applied a voltage is induced into the converter wire.

What I believe is happening is the electric brake controller puts out a pulse of electricity as it is a pulse width modulator. This was confirmed by a handheld oscilloscope. This then induces the same voltage in the parallel wire which is the converter wire which the oscilloscope confirms. The voltage according to the oscilloscope is 17V peak. Which would explain why the converter diode burnt up.

So I need to run a second wire on the opposite side of the truck to make sure the brake controller does not create problems.

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