How to test a switch

[pbsk8er03]

I have a dpdt switch that i am pretty sure is bad...How do i test it with my multi meter to be 100% postitive??? I have  a radio shack multi meter and it doesnt have the beep function on it just to let ya know

[petemoore]

For a super kwik light indicator continuity tester, take a 4k7/LED circuit, ...connect it to a battery so it lights [the LED is polarity sensative], then open the circtuit...where you opened the circuit is where you connect your probe leads...alligator clips are nice since you have to look at the light to check continuity.
 You won't blow the switch up, but might have to be very slightly careful what you're connecting 9V to with it...you can get an LED to light with lower voltage than 9V...you will probably never have call to use it where it could say reverse bias a transistor or something like that.

[Dave Z]

If your MM has an Ohms function, use that.

If it reads the same when you connect to the terminals as it does in open air, the switch is open.

If it reads something small like .01 ohms, then the switch is closed. If it reads a few ohms maybe you have a dirty contact in the switch. Some switches like the one in a les Paul can be cleaned (open) some cannot.

[pbsk8er03]

umm does any 1 wanna tell me how to do it with a multi meter cause i dont have a LED and 47k lying around

[petemoore]

Tha's 4k7/LED or 4.7k
 The ohmeter is a good way...the switch open should read the same as the meter's leads floating, the switch closed should read like the ohmeter leads connected.

[Hal]

the resistance when the switch is "on" should be close to 0.  The resistance when its "off" should read "infinite," different depending on the DMM.

but be sure to jiggle the thing around while testing.  Just becuase it works when you test it, if you suspect its a bad switch, it might not always work.

[Paul Marossy]

I use the conitinuity checker on my DMM. If it beeps when it shouldn't, then there is a problem.