post up a pic, if the whole mirror has a yellow hue it might be that the heating element changed the color of the fluid, whether that means it works or not i dont know.

the heated mirror function comes on as needed (or Quicksilver might have the reference page to how it works) as far as i can tell, when i bought my X both mirrors had some delamination of the glass, i posted up recently that i purchased heated, blue tinted aspherical blind spot mirrors from our friends in Latvia and am thoroughly pleased.

Not sure though on your situation as i do not have auto dim function

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards