6.9 or 7.3?

[SuperDave]

A pyro probe is a thermocouple... will produce a millivolt response when heated.

Not sure if the Banks gauge direct-reads the millivolt signal, or uses a module to step it up to a 0-5V signal (for example). In the case of the latter, the gauge is 'dumber' and you could feed it an appropriate voltage directly as a test. Beware, you can easily cook you gauge applying the wrong voltage to things.

The probe is a thermocouple huh? Like on a gas fired furnace or water heater, produces a very small current when heated, I truthfully did not realize that but it makes perfect sense. Thanks for that info! The gauge has 3 wires in (12v+, ground and 12v for the light) and wires 2 out that go to the thermocouple. There is no driver module like many others. This pyrometer is old I'm guessing '86 or '87 so it probably doesn't owe me any service anymore but if I can do some tests on it and possibly repair it that would be great.

 

[The_Josh_Bear]

So glad to hear that you tore into it and found the problem! Glad I could help, too. Thats got to put a smile on your face every start-up.

As for the Pyro, the easiest way to tell if the gauge is bad that I can think of is to pull the wires out from the probe and check the millovolt reading. Then start the engine and check some more, the reading should increase as the exhaust heats up. If it stays the same, your issue is the probe. Mine died after 6-ish years of service, found one on Amazon for $16 and it's doing well.
They are type-K thermocouples for your googling pleasure.

Happy wrenching!