low pressure air alarm not working properly, ADVICE APPRECIATED

That 10.8v is just ghost voltage on the ground circuit from the ICU.

And you are right.... you need two normally closed switches to make the external buzzer work. The factory switches are normally open.

Brain fart on my part, with the factory switches in place, wiring it like I showed would cause the buzzer to come on above 60 lbs of air.

 

You'd need two of these to make the external buzzer work...

Pressure Switch 60 PSI Normally Open Floating Ground | Pressure Sensors & Switches | Senders and Sensors | VDO Instruments and Accessories

 

Whoops, and there I go making a wrong choice again. That’s what I get for trying to think while tired. For the external buzzer to work, you need NORMALLY CLOSED, so it opens the circuit when it gets to 60 psi and shuts the buzzer off.

That would be the 560

 

My ICU just crapped out again and this time grounding the pin doesn’t shut the light off. I’m going to re-cap it and see if that does the trick. Other than that, I may end up reengineering the light and buzzer. I’m not spending $700 on a refurb unit when I probably ain’t staying in this game much longer anyhow.