Testing small switches without desoldering

[Selix]

I have a few small switches and a multimeter, but desoldering each one feels like a hassle.
Is there a faster way to check if they’re functioning without taking them off the board?
I’d love to hear any tips, tricks, or clever setups you might suggest!

 

[shimmilou]

With all power off, measure the resistance across the switch. In one switch position you should read zero ohms, a short, and in the other switch position read some other unknown resistance that will likely be a much higher ohms reading. If you see a difference in resistance after switching, then the switch is likely functioning correctly

 

[barfle]

Like @shimmilou said, switches that are closed (on position) should read close to zero ohms up to their rated current - far less than one ohm, especially for “small” switches like DIPs.

Without removing them from the circuit, there’s likely an unknown amount of leakage around the switch that would result in a finite resistance when the switch is open or off.

 

[Selix]

Sure, that's the tough part sometimes you’ll still get ghost readings when they’re off. Is it a good approach if I perform a quick continuity test using a multimeter set for continuity? This way, I can check whether the switch is open or closed right then and there. Just a thought

 

[barfle]

Sure, that's the tough part sometimes you’ll still get ghost readings when they’re off. Is it a good approach if I perform a quick continuity test using a multimeter set for continuity? This way, I can check whether the switch is open or closed right then and there. Just a thought

The concern I would have is that a continuity check has a threshold that you probably don’t know. By that I mean there is a resistance below which it will indicate continuity, but you probably don’t know what that is, and your circuit may have a resistance lower than that around the switch.

I know of circuits where DIP switches short out resistors in a ladder, and some of those resistors can have low values, approaching one Ohm. I doubt if a continuity check would tell you that the switch was working.

Comparing the actual readings between “off” and “on” can tell you if the switch is good, but you may have to set your scale for very low values. “Continuity” checks won’t do that.

 

[Selix]

Good point, absolutely agree, continuity checks can be a little too general for these low-resistance situations. It’s definitely more effective to compare the actual readings with the right scale to make sure the switch is functioning as it should. Thanks for the valuable input