The rear parking sensors were not working in my car so decided to take a look. All the sensors were clicking away happily so next thing to check was the sounder under the dash. I took the sounder out and popped it open. I then checked the little speaker inside and it was open circuit. I sourced one that had similar, although not exact specifications and ordered it. It was the closest in spec I could find at short notice. Soldered the connections and reassembled the sounder. Back in the car and bingo, I have parking sensors! Total cost of fix £2.99. Worth checking if your parking sensors stop making any noise.
