Back up monitor

The speaker on my back up monitor doesn't work. I've got the volume up on high but when hooking up the boat, the wife stands behind the motor home and tells me when to stop. I can't hear her through the monitor speaker, no sound at all. Any advice?

  Lynn

Mine stopped working many years ago.  For the life of me, I can't figure out where the microphone in back is located.  I figured it could be a pin hole that needs to be cleaned out.

I did not know there was a microphone.  Actually I'm sure there is not on mine, at least I have never heard anything from it................

Our sound was exceptional to have.  I really wished I could get it working again.  It worked great for about 5-6 years, then suddenly went silent.

Irene standing behind would provide both voice commands and hand gestures when backing up.  Since the failure I am limited to hand signally alone.  Irene still provides voice commands but doesn't help me anymore.