Wiring a Mechanical Siren with a "Single Lead Switch"

[aggmeister2010]

Hello everyone,

I have an antique car, and I'm installing an antique mechanical siren on it.  I ordered an antique momentary switch to try to make it look period correct.  Oddly, the switch only has a single lead, similar to this:

http://www.aliexpress.com/store/product/Single-Lead-Wire-Momentary-Action-Car-Auto-Engine-Stop-Switch-12VDC/1846805_32310960617.html

I'm trying to figure out how to wire it up.  My assumption is that the threads are the ground, and the single lead is the hot wire?  It mounts to a metal dashboard, so I suppose I could just wire it in at the end of the circuit, like so:



Thoughts?

 

[shues]

That's an engine stop switch.  I used something similar on a lawnmower with a broken throttle cable.  I wired it in to ground out the spark plug and kill the engine.

The single lead is continuous with the mounting bracket when the switch is depressed, and is an open circuit when the switch is released.  I believe that it would be correctly called a normally open momentary single-pole single-throw switch.

Instead of switching the positive side of the relay (or solenoid, depending on the number of amps your siren draws) switch the ground side.  Something like this:

 

[aggmeister2010]

Actually, that works even better...I won't have to run much wiring at all!  I can keep the relay, siren, and fuse all in the same area with short runs of wire, and then just run one cable to the momentary switch.  Thanks!

 

[wilsonbr90]

Shues has it spot on. only change I'd make because I'm anal is that 85 should be the ground and 86 the power. But same results either way

 

[aggmeister2010]

Wired it up just like y'all said, works like a charm. Thanks!