[fastfredracing]

. I cannot seem to find this vacum switch for my old tow truck project . It is a 1977 Chevrolet c 60. Has vacum brakes, and a vacum switched 2 speed rear end.
I'm pretty sure it is supposed to alarm if the vacum goes under 8 hg .
Mine ist kaput, and just alarms randomly, and all the time while driving. It is really loud and annoying . It is also required , so I have to fix it .
I have full vacum, and no leaks, verified, by 2 onboard vacum gauges .
It looks exactly like any other 2 pole pressure gauge used on cars for as long as I can remember.
When I search for it, only pressure switches come up. I have randomly searched for several months now, and have not found one yet.
Will a pressure switch set for + hg, also close, and alarm for the same amount of - hg?
Im stumped.
Here is what it looks like. Threads into a little t fitting tied into my vacum booster vacum feed line.

Have any ideas where to find such a thing ??