Passenger Audio Problem

[midsouthps]

I have PMA 450B in my wife's C172. After recent annual, the rear passengers cannot hear the crew. Setting is on "All". I can hear the two rear passengers but they can't hear me. I think one of them said they could hear me when I I had the PTT engaged (talking to ATC). Does anyone have any idea of where I start looking for a bad connection?

 

[Ray93J]

 

[midsouthps]

 

[Ray93J]

 

[sgavette]

 

[midsouthps]

 

[Ray93J]