peterbilt air leak

would anybody happen to know what pressure switches do what or a scematic of a 1988 379 air manifold behind the fuel petal?i have a small air leak on a low pressure switch, i rdmoved it and plugged for now but cant figure out what it does! my bk lights work off spike n petal, low air lights are good, interaxle light good, fan etc

 

that is what the switch looks like and the location is the very right rear or back side of the manifold , was wondering if tge engine idel timer uses one of these?

 

the low air light works , buzzer never has so that could be, if thats the case it can stay plugged!

 

ya im thinkin its a buzzer , i havent noticed anything not working, thanks for the replies