Anyone know what this is? It came out of a furnace and I need to find a replacement part

File: 20160110_204405.jpg (2MB, 3264x2448px) Image search: [Google] [Yandex] [Bing]

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Pic 2

>>30317
check the shield on the back

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>>30317
It's a pressure switch.

But you'll need to replace it with the exact model, which you can find by googling "<your furnace> pressure switch" or whatever identifying numbers are printed on it.

Actually, how d'you know you need to replace it if you don't know what it is?