Calibration of the compass in my mirror

HI guys I have just installed an auto dimming mirror with a compass, the dimming on the mirror works really well (much better than the 2000 part did). So here is my problem.

The mirror originally came from a 2004 A4 and I am not sure the compass is working properly. I know the ones that were fitted to the A6’s required calibrating and I have the instructions to do that. However their I no button to press to calibrate the mirror. Has anyone dealt with the type of mirror that I am taking about and knows if it needs calibrating?

Thanks
James

 

I replaced my mirror a while back. Had a letter C on the compass area. I did once read instructions on how to calibrate it, but essentially you just drive round and round, and it seemed to sort itself out. Do a search again, and you will probably find it.