Odd electrical question

[Brucep 0]

A friend replaced a togle kill switch (spst) on a Tecumceh engine on a go cart and it works opposite of the lable. Turn swith to on and it kills the engine, off and the engine runs. We figure the wires are connect backwards, so we swap them and it made no difference. Switch worked the same, off it runs, on it stops. We tested the switch for cotinuity when in the off position and continuity is there, switch it to on and continuity is not there. Good switch. Ok, this part is even odder, atleast to us. We cut the wire 6 inches or so after it protrudes from the engine shroud (points) and with the engine off we tested the wire for continuity with the frame and we have continuity. So, the engine should not run because the points are grounded. Right? Wrong... we pull the rope, the engine starts, then we ground the wire directly to the frame and engine quits. Just like it should. Does anyone know why the switch works backwards, and why the engine runs when it appears to be grounded all the time, but, when you do ground the wire the engine quits? It has three of us stumped. I didn't take the shroud off to look at points and connection, if I had it here I probably would.

[John_RI 3]

Why not simply rotate the switch 180 degrees?

[HubbardRA 19]

If you tested the wire with the points closed, it would show ground. If the points were open then it would show open. The switch keeps it grounded all the time when in the off position. The engine fires when the points open. With the switch grounding the wire, the points cannot break the field in the coil and cause the ignition to fire.

[firefoxz1 4]

The switch you bought is closed when "on" (which the way switches are normaly used) so when in the on position it is grounding the ignition out shutting the engine off. Nothing strange there. I believe the ground wire will always have some continuity to ground in a system because of the condenser but will definitly show when points are closed. How old is this engine to still have points in a Go Cart?

[D-17_Dave 12]

It doesn't matter how old the engine is, or whether it has points or electronic ign. What matters is grounding the secoundary circut of the ign. system to kill the circut. Whatyou had was a normally open switch, what you put back on it is a normally closed switch. You can cheat and break off the tab on the ON/OFF cover and rotate the switch. Or peplace the switch with the first style, a normally open switch. There's nothing wrong with the engine, or the switch you have. There is a problem with the application your asking it to do. It's simply just the wrong switch.

[Brucep 0]

Rotating the switch wouldn't matter it still would work the same, just like swaping the wires from one terminal to the other and it still works the same. Maybe that is what you meant. Relabling the wording (on/off) would do it. Although he could make it work, we still wondered why it worked the way it did. I do realize a closed circuit is ON or ENERGIZED and an open circuit is OFF or DE ENERGIZED. I never thought about the "type" of switch, although I do know and understand them. Just never gave it a thought. The wire showing continuity to ground makes sence when the points are closed. We didn't think about that either. The engine is old. I don't know how old without looking up the numbers but my guess is 15 or 20 years. It's on an old go cart. Sometimes you just need an outsider to open your eyes. Thanks guys! I can see clearly now.

[John_RI 3]

I guess I was thinking that you had a toggle switch mounted in a dash with the labels on the dash. I thought the suggestion of rotating the switch would solve your problem of the incorrect on/off state, unlike changing the wires which (as you found) will result in no change.

[Brucep 0]

Ok, I see. Yes, the labels are part of the switch which is notched so they can only go one way. But yes, if they were just on the dash that would do it.

[KVANDY12 0]

Bruce do you see how simple it is now. Don't feel bad I did the same thing on my grandson go cart switch. Bought the wrong one to, like you. But I took it back to the store and told them it didn't work right, they then gave me the right one. So I guess the lessen there is a switch is not always the right switch by the way it looks.

[HubbardRA 19]

Bruce, More than once, I have filed off the tang on the on/off plate so that I can reverse the direction of throw on the switch to match other switches or the original mounting scheme.

[Brucep 0]

Yes, I do see, it's not all that hard to understand. Quite simple actually. Just some things you don't really put enough thought into befor you head off in the wrong direction. Thanks again everyone!