Aux backup lights help: SPDT switch to relay, how?

[yob_yeknom]

With that setup, it is possible for you to have the switch on and the stock reverse lights on at the same time. That will cause double the current to go through the relay and could fry it.

How come you don't want a 3 position switch? Don't you want to be able to turn the lights off when needed, even if you're in reverse?

Say it's dark out. You just crossed a stream or small river. You can't make it up the other side for some reason, and now you have to back through the water. All that light making a big reflection could blind you and have you swimming... :roll:

 

[Okrazie1]

John, having the two voltage sources (the switch and the back up lights) in parallel feeding the coil would not cause the coil of the relay to burn up. The voltage applied to the coil would not change, and since the resistance of the coil has not changed, the current through the coil would remain unchanged. If the voltage sources were in series it would be a different story.

 

[yob_yeknom]

(been a while since I was in an electronics class)

But I thought amps went up in parallel. And isn't it the amount of amps, not voltage, that creates heat?