ntsqd
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Switching the ground is actually a pretty good way to wire some relays. Computers and PLC's commonly do this (your engine's fuel injector solenoids are switched this way) because the voltage drop has already happened in the load and the computer or PLC won't be switching the full power of the circuit (P=V*I).
If you are only interested in a switch in the cab to turn them on and off this would be a good option. As a bonus the failure mode (a short) just turns on the lights rather than blowing a fuse.
The problem with trying to do this when using the reverse lights to be one switching mode is that you don't have access to the ground side of that light circuit, only the hot side.
The general down-side, in my opinion, to switching this way is that it is uncommon, which can confuse any future trouble shooters. I don't see this to be too big on an issue, but it does have the potential to be one if the person working on the circuit isn't familiar with the method.
If you are only interested in a switch in the cab to turn them on and off this would be a good option. As a bonus the failure mode (a short) just turns on the lights rather than blowing a fuse.
The problem with trying to do this when using the reverse lights to be one switching mode is that you don't have access to the ground side of that light circuit, only the hot side.
The general down-side, in my opinion, to switching this way is that it is uncommon, which can confuse any future trouble shooters. I don't see this to be too big on an issue, but it does have the potential to be one if the person working on the circuit isn't familiar with the method.
