VXR8 temp gauge fault

[fabtech04]

Has anyone come across this fault 2007 Ls2, Temp gauge dropped to C while driving, contact dealer X comes up and loss of A/C, fault will then suddenly disappear, my be fine for a few days then may happen again then stay for longer.
Thinking it may be temp sensor related, waiting to plug into diag machine to see if any DTC logged. Any ideas would be appreciated.

[fabtech04]

No belt is still on and A/C works as soon as the gauge works again so seems like it is connected to sensing system some how.