I suspect this switch isn’t functioning correctly and would like to replace it but can’t find one similar. What sort of switch is it?

The front is a push with two states (in/out) and has a bulb to indicate on/off (though that’s not currently working). It’s probably from early 90s or late 80s.

enter image description hereenter image description hereenter image description here

This is a similar switch that I got a better photo of, though it has extra wires out. The switch of interest is in the background.

enter image description here

  • \$\begingroup\$ The [RS] logo is the central hint here: rs-online.com \$\endgroup\$ Mar 13, 2019 at 15:58
  • \$\begingroup\$ @MarcusMüller yup, no part number though. I have had a look at rs-online but couldn’t see a match, hoping someone else with more knowledge of what they’re searching for may have more luck. \$\endgroup\$ Mar 13, 2019 at 16:00
  • \$\begingroup\$ I have found similar looking ones such as this but there are several that look identical that have different descriptions. \$\endgroup\$ Mar 13, 2019 at 16:13
  • \$\begingroup\$ It looks like it may be energizing a relay through the bulb. I could see doing that if it were essential to safety to only energize a circuit when the bulb was lit -- running a relay coil through the bulb would insure that a burnt-out bulb de-energized the relay. If that's the case, then replace the bulb and you'll be back in business. \$\endgroup\$
    – TimWescott
    Mar 13, 2019 at 16:20

2 Answers 2


The diagram on the side is pretty clear -- the top terminals are for a bulb, the "middle" (one up from the bottom) terminals are a NC contact, and the bottom terminals are a NO contact. It's almost, but not quite, a SPDT switch -- it's more like a DPDT switch that's missing some terminals.

BUT looking at the picture, it's running current from the contacts through the bulb. It may be that the burnt-out bulb is an essential part of the circuit (possibly for safety reasons, to never energize a circuit unless there's an indicator light).

Dig through the rs-online site; this should be pretty obvious.

If all you need is a replacement, and looks don't matter, then by the diagram and the wiring, only the NC section (and possibly the bulb) is being used -- so you just need a normally-closed (or closed-when-out) SPST push-push switch with a bulb.


It’s either a momentary or toggle push-push latching switch . What makes you think it is not Functional?

They do make cheaper ones too. https://uk.rs-online.com/web/p/push-button-switches/0319449/

  • \$\begingroup\$ It’s latching rather than momentary. The continuity didn’t seem right, might be because we didn’t realise the type of switch. \$\endgroup\$ Mar 13, 2019 at 17:36
  • \$\begingroup\$ How does it feel? \$\endgroup\$ Mar 13, 2019 at 18:05

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.