It took me awhile to figure out that problem on my car.
The posts from KC and Sir Ringlee are correct.
My car has heated mirrors, but had the simple switch.
I don't know if the PO changed it or what or why?
The simple switch has one single symbol , one light
and 3 connectors on the back.
The dual switch has 2 symbols , 2 lights and 4 connectors.
I have always a problem to peek in the mirror housing.
To remove the mirror itself is easy.
On the bottom is a hole in size of a fingernail.
Poke a screwdriver in, with the longside of the drive
along the long axis of the car, or better speaking
the flatside points sideways.
Imagine there is a kind of 2" wheel, what you have to
turn to the outer side of the car to release the
4 notches whitch hold the mirror.
The dual switches are hard to find at the junkyard.
Also the heated mirrors are rare.
The complete unit has a different electrical connector
in the doorpanel, but I'm not sure if it differs from
year to year or just the models with heated mirrors
have a different connector.
My PO glued ordinary mirrors over the broken original.
Now I repaired it all.
my .0001 cents