Car: 2006 1.8 ES petrol v-tech
Join Date: 13th March 2015
Thanked 42 Times in 37 Posts
I think the polyswitch within the sod, the part that fails, works by heating as the voltage passes through it to the point where it cuts off the power after a predetermined time, so if it heats too quickly the mirror stops part way or conversely if it doesn't heat quickly enough the mirror goes beyond the stop.
Someone with more knowledge might correct me on this!! But it's worth changing over the sod from the other mirror to test.