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I am trying to replace a burnt out illuminated rocker switch in an electric fireplace heater. I ordered a replacement switch that looked like it would do the trick, but failed to notice that it had three terminals, while the original switch has only two.

Original Switch

There is no pinout on the datasheet, the terminals are simply labelled 1, 2, and 3. I looked into this and the third terminal is usually ground, without which the switch won't light up.

Is it safe to ignore ground / bend it out of the way? As you can tell by the linked picture, there is no way I'll be able to plug in the wires with the close arrangement of terminals on the new switch. The light won't work but I can live with that. Or would I have to find and order a two terminal rocker switch?

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closed as off topic by Leon Heller, Kortuk Mar 7 '13 at 14:02

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  • \$\begingroup\$ My bad... I did not read this exchange's FAQ before posting. It is a pity that there's not an exchange for this sort of questions though - I got a very informative reply that helped a great deal. \$\endgroup\$ – Stan Mar 7 '13 at 13:11
  • \$\begingroup\$ @LeonHeller the question is clearly not about the domestic (domestic, I think you meant consumer) product. That's only ancillary to the real question. \$\endgroup\$ – Passerby Mar 7 '13 at 13:26
  • \$\begingroup\$ @Stan it's hard to tell, since 2 terminal illuminated switches are not common at all. The picture is small and out of focus so we can't tell what the markings are, to possibly find a datasheet. You don't know if the internal light is a led, or a bulb/lamp, if the circuit the switch uses is dc or ac, or depends on the light to internally limited/resist the circuit. Since it is a electric heater, the entire thing might run at Mains 120v the entire way. Adding in a simple spst switch might not work. Since the switch is dead though, you can take it apart to see how it is wired/built. \$\endgroup\$ – Passerby Mar 7 '13 at 13:33
  • \$\begingroup\$ @Passerby The "original" image clearly shows an embossed "16A 250V AC". \$\endgroup\$ – Anindo Ghosh Mar 7 '13 at 13:46
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The replacement switch is a Single Pole Single Throw switch, just like the original. However, the bottom terminal connects the illumination light, unlike in the original where the illumination switching is internal.

From the datasheet it appears that the function of the middle and upper terminals are the same as the middle and lower on the original switch. This is easy verified using a multimeter, or a continuity tester of some sort.

(You can jury-rig a continuity tester by opening up a simple torch, and using its bulb, and its batteries, hooked up with a couple of pieces of wire via the switch terminals.)

Once this is confirmed, you could try bending the illuminator terminal (either the top or the bottom one, whichever is the illumination tab as verified above) out of the way and covering it thoroughly with insulating tape, then wiring up the switch just as the original was, with the center and the remaining end terminal.

Making the illumination work would need an additional piece of wire between the top and bottom terminal, properly insulated after hooking up, of course. This may best be left for a more experienced person to deal with.


For those who haven't examined the image posted in the question as the "original switch", here is a straightened, cropped, image-enhanced version of the switch, clearly stating "16A 250V AC".

Original Switch

This is why the solution given above is clearly valid.

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    \$\begingroup\$ Without knowing if it's a 12v dc circuit or a Mains circuit, or if the switch affects the circuit more than just a on/off (if it depends on the switch's internal lamp to regulate the load for some reason), this isn't the best advice. \$\endgroup\$ – Passerby Mar 7 '13 at 13:35
  • \$\begingroup\$ @Passerby Both switches are 250 Volts AC, as per the image / link. Internal lamp regulating a load? The lamp is always in parallel so that it works even if load is not connected. \$\endgroup\$ – Anindo Ghosh Mar 7 '13 at 13:45
  • \$\begingroup\$ @AnindoGhosh how would a two terminal switch with a lamp be in parallel? \$\endgroup\$ – Passerby Mar 7 '13 at 15:27
  • \$\begingroup\$ @Passerby Interesting and valid point - I can only think of some unduly complicated approaches, highly unlikely to be used in a mass-produced switch. It might be useful for OP to tell us whether the existing 2-terminal rockers do illuminate at all, or whether they illuminate only when drawing current. \$\endgroup\$ – Anindo Ghosh Mar 7 '13 at 16:31
  • \$\begingroup\$ I took @Passerby's suggestion and tore the old switch apart ...and it doesn't light up. It looked like it did, I thought I remembered it lighting up, but I was wrong. Sorry for wasting your time guys :$ \$\endgroup\$ – Stan Mar 7 '13 at 18:35

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