Recently my Sounders have stopped working.  If I put the system into alarm, I get 0V at the sounder and when I measure across the terminals at the panel. If I remove the wires from the sounder terminals at the panel it measures 12V. Don’t understand what’s going on? Any ideas?

Depends where and what terminals your testing.

Also what panel and type of sounder(s) would be helpful.

For external sounders there is a constant hold off voltage plus a negative trigger.

 

It’s a paradox system. It won’t let me upload any photos. 
 

At the sounder I have a set of terminals labeled siren + and -. I measure across them when the system is in alarm and it’s 0V. I have strobe terminals labeled + and - and I measure 12V Dc. 

Are you in the UK? Not a brand seen here.

It could be the output is blown if it's been overloaded?

Put 12v on the sounders see if they work?

2 hours ago, sixwheeledbeast said:

Are you in the UK? Not a brand seen here.

It could be the output is blown if it's been overloaded?

Put 12v on the sounders see if they work?

via a fuse...

 

If your disconnecting the sounder and it showing 12v in alarm then you either have a knackered sounder or cable issue. Have you metered the cable?

Was thinking a battery but yes not the system incase the devices are faulty.

 

1 hour ago, sixwheeledbeast said:

Was thinking a battery but yes not the system incase the devices are faulty.

 

agreed but if its in short, putting it across a battery with no fuse will spark a lot...

Would say you have common sense for that... sparks and hotness would be a bad time.