Range l322 external temp gauge

I know this may sound a little insignificant but i wish to change the read out from Fahrentheit to Celcsius.I have searched the owners manual and workshop manual but had no joy.
Its an 02 td6
thanks
http://www.wbuf.noaa.gov/tempfc.htm

welcome to lz, i think its behind the grill to the right as you look..

Hi its the actual readout on the dash i I want to reset. The sensor is behind the RR badge on the grill as you say Its working fine only its set in Fahrentheit mode.I pessed the reset buttons on the dash by the clocks ( dont ask why ) in conjunction with the ignition key in different positions and after it had changed to Fahrentheit from Celcsius.

JOB DONE
Pressed left reset button for 5 seconds with key at position 2 then pressed another 3 or 4 times till temp gauge showed up as celsius turned of key, job was done