low pressure air alarm not working properly, ADVICE APPRECIATED

If the chime is too quiet, that may be why someone wired in an external buzzer.

Leave the external buzzer out of the equation for now.

Tilt the instrument cluster back and look at it from the top down. The smaller connector on the left is the one you need to look at. The row of holes that are closest to you... count from the left to the third hole. Is there a wire in that hole? It should be labeled 18, is that the case?

 

That looks like one of those Radio Shack piezoelectric buzzers. You can still make that work as the buzzer, but then you’ll need to ground the wire coming out of the ICU to make the factory chime stay off.

The external buzzer gets 12v on the red wire and route the black wire through the two switches to ground. Get the 12v from a power post in the fuse panel, DO NOT tap into a wire under the dash to get power.

 

In your diagram, the buzzer isn’t getting any power because you have both sides connected to ground.

 

The wire coming from the ICU and going through the two switches is a ground wire. The small amount of voltage you see... ignore it.

Think of electricity in terms of water flowing through pipes... the ground point is the drain. The two switches prevent the water from flowing to the drain until the air pressure is above 60 lbs. Make sense?

 

If you want to use the external buzzer, wire it like this...



But if you do it this way, you also have to cut the wire coming out of the ICU and ground it to make the light and factory chime stay off.

 

Unhook all the factory stuff and use all new wire. The ground point can be anything metal under the dash.