rear defrost function, and its switch and illumination

[Ken Keith]

Hi,

Now that it's chilly in the mornings, I sometimes need to use my rear
window defroster.  When I use it, sometimes I can't tell if it is
working.  When this happens it's probably not working, because other
times it's quite obvious that it is working.

The illumination on the defroster switch is intermittent, both the red
icon of the defrosting window, and the triangle that illuminates when
you activate the switch.  I am wondering if illumination of the
triangle is related to the intermittent operation of the defroster
itself.

When I press the button down, the triangle lights up on its way down,
but then goes out when the button is in the on position.

I'd like for the defroster to work correctly, as well as the two types
of illumination in the switch.  Is there a documented DIY repair
procedure somewhere I can follow, and does anyone know if the lighted
triangle is related to an activated defroster circuit, the way an
illuminated diff lock on some Audis is confirmation that the diff is
actually locked?  Or is the lighted triangle failure independent and
unreleated to the defroster failure?

Thanks,

Ken