V16 Volume good at startup, then within minutes drops away

[maxcochrane]

My V16 with a Razor head has been working well for many years.
Now on startup and switching on avionics volume is good. I can hear the ATIS loud and clear.
Communication with the co-pilot headset experiences the same drop in volume.
By the time engine has warmed up the volume drops away (can be just heard at idle but in flight is barely audible).
When engine is warm on startup it will have good volume for about 15 minutes before volume dropping
Has anyone experienced this and any suggestions to try and fix?
I have not tried another Razor at this time. Cannot get one to try for a few more weeks.
There does not appear to be any loose connections.

[sparxfly]

If all communication volume (VHF, intercom, etc) in both pilot and copilot falls off I would suspect the V16 audio output is failing.
If just one headset it will be that headset or its wiring.
Fancy noise cancelling headset- battery failing?
Unlikely to be the Razor head.

[maxcochrane]

Thanks Stuart for replying. With further investigation we discovered a nick in the 2 core shielded wiring going to passenger headset. Wiring replaced and problem solved. The nick was caused drilling a hole under instrument panel to install a Ram mount. The problem we had finding the cause was made difficult because of the way the volume would drop. initially the volume would drop within minutes into a flight. With many trials switching on the avionics without the engine running, volume would be normal and within minutes the volume level would drop significantly. By moving the wiring loom to the Razor head the volume could be restored briefly. This was traced to the headset wiring near the Ram mount.