I have a vent hood over the cooktop with a bunch of switches and indicator lights
for the tanks on the front vent fan panel. The water pump switch is located there. I like to be sure to know when the water pump is switched on so as not to leave it on by accident when I leave the trailer of go to sleep. I guess I'm just cautious about a leak happening and the pump draining the water tank in an unwanted location! So I decided to replace the small on/off toggle switch with one that lights
up when on. I was able to pry the single switch out of the front of the panel with a knife and was surprised to see three wires, as I'd expected to just see two wires, hot and load. The new switch also has a place for three wires (hot, load and ground). It needs a ground for the light
in the switch to work and the other two wires are just hot and load. I was perplexed to see 3 wires on the old un-lighted switch but hoped that for some reason it happened to have a ground also, which would have made my task a lot easier. But not so ...no ground wire. One was a hot wire and another a load wire, but I couldn't figure out the third wire. I removed the old switch and hooked up the hot and load to the new switch and it turned the water pump on and off but no light
. So I ran a temporary wire to a nearby ground, and voila! The switch lighted when the pump was turned on like it should. I then tested the old switch which I had removed, which was either on or off, but found that it switched the hot lead between the other two terminals! So I am totally puzzled about what would the other wire that receives power when the water pump switch is OFF go to? There was a separate 3 wire harness going only to the water pump switch with a 3 pin plug about 8 inches away from the switch, so it wasn't just some after-the-fact cobbled wiring mess. I just unhooked that third wire and taped the end. I'd appreciate it if anyone has seen such a thing or can even hazard a guess as to why the water pump switch would be an "either or" power switch and what it would power when the pump was in the off position. Thanks for the assistance.