A bit puzzled

[scarecrow]

I was fixing a broken exhaust on my digger today when I spotted this thing and was wondering what it was it's connected to the pipe between the air filter and the air intake for the engine my first thoughts were it was a heater plug but it doesn't look like anyone I've ever seen before

there are two connections for wires I took it off and tried it needless to say it doesn't work and there is no sign of any wires that connect to it anywhere


it's an old ford 555 has anybody any idea what it's for or seen anything similar

 

[snowcat]

looks like the vacuum minder, switches the light on when the filter gets clogged, harvesters/crushers etc working in really terrible conditions have a manual minder, and an electric one running up to the EMU, it probably is supposed to trip at around 20-25hg......

 

[Luke]

as above, looks pretty tired to me though

 

[wyn]

They are so big because you need the surface area of the membrane stretched across the diameter to operate it and make the connection between the contacts.It should also have a small hole in the side opposite the connections so you only have atmospheric pressure on that side, if i remember rightly.
You also see them as little spring loaded units that show a red marker when the filter is blocked.

 

[scarecrow]

now that makes sense I was thinking it didn't look like a heater plug
never heard of a vacuum minder before and I knew I could depend on ye guys can solve the mystery

As for looking tired I'll have you know that digger is only in it's med 20