Thermometer in mirror

That outdoor temp thermometer in the RV mirror on my Suburban has gone flakey on me. Occasionally it works right, but most of the time the temp's around 125 (even when there is snow on the ground). The compass works fine.
I'm guessing it is a problem with the sensor or grounding. Anyone know where to find it? I can't seem to find any wiring diagrams. I believe it is in the engine compartment. I really love it, but not enough to plunk down a few hundred $$ to the dealer for a new one.
Thanks!
Gary
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fine.
where
the
In front of the radiator. Very visible on my Sierra (Duramax with three radiators/coolers). Follow any wire going to in front area. Could be from top or bottom. On the Sierra the wire come in from the bottom and sensor is on a bracket in the middile. On a Safari wire comes from the top but the sensor is near the bottom.
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Great! I'll check it out, thanks.
G

temp's
from
the
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