We got a Gentex Auto Dimming Rearview Mirror with our 2350 S. The mirror includes compass and outside temperature function. The compass function tells you where you are headed: N, E, S, or W. It works fine after we did the calibration procedure in the manual to adjust for local magnetic variance. The compass is useful particularly after a turn when you need to know if you are headed in the right direction (I.e., before our GPS starts bleating, “Recalculating!”).
The outside temperature function is redundant with the same information on the Sprinter instrument cluster display. On the Sprinter, you can choose between displaying the outside temperature or your speed. I like the mirror display. It is easier to read because you do not have to find the info in the clutter of the instrument display. Unfortunately, our mirror display did not read correctly from the get go. It would be OK when starting out cold but after a few miles, it would read 15+ degrees too high. Obviously, the engine heat was influencing the sensor.
I could not fix it until I could find and move the sensor. Another member let us know where it was (See: http://phoenixusarv.com/community/index.php?topic=167.0
) The other day I unclipped the sensor from its location on the driver's side fender liner near the engine and moved it to the location specified in the manual: in front to the radiator, more that 8 in. from the pavement and away from the headlamps. Note: On the Sprinter I had to loosen the grill to be able to get my big hand in position to attach the sensor clip low on a grill bar.
The mirror temperature display works correctly now.