Cars - 99 Service light on (wrench light, not service engine soon light)..help!!

Ok, so earlier today I was having battery trouble, and let my car idle
in the driveway for about 15-20 minutes after coming back from the
store, so that I wouldn't have to get a jump because I was leaving
again soon...I went to get in my car, and smelled something burning,
similar to that of brakes, but more like electrical...I got in the car
and noticed the temp gauge was up about 3/4 of the way, which is
unusual, its never gotten that high and its 5-15 degrees outside in
northern michigan....anyway, the service light was also on, I
immediately turned the heat on full blast, and drove the car, and the
temp went down to normal. Went to autozone to have the codes read, and
it came back with nothing...went to the local garage and had them check
the battery and alternator, and said everything was fine, and that it
must just be the cold cold weather we've had lately that was keeping
the battery from starting the car...anyway, what could cause that foul
smell? I've driven the car for about 100 miles, it drives normal, i've
smelled that electrical/brake smell once when driving down the road for
about 20 seconds, and then it goes away...any ideas of what to check?
Next steps to take? Perhaps the fan quit working and the motor burned
out? How could I check the fan? Any ideas are greatly
appreciated...thanks!