Temp Gauge Behavior

[Martin W. N. Suryadarma]

Hi everyone,

I have a question that has been bothering me for a while. My car is 1989
Audi 100

In the summer, my engine temp usually goes up to the middle line and the
fan will kick in. It stays around the middle during city driving. If I go
to highway, it can go down to the line before the middle one. BUT, if I
have air conditioner running, the temp will never go as high as to the
middle line. It seems that the air conditioner makes the engine run
cooler, which doesn't make sense

Now in the winter, the same thing happens. During city driving it gets to
the middle, then fan kicks in. Of course, I'm in Philly, so it's not that
cold yet here. BUT I just noticed, if I have the heater on, the temp is
really low, it's only around the 1/4 mark, and doesn't move up during the
same driving condition. 

So does a/c and heater running make the engine run cooler? Or radiator is
cooler? No right? BTW the car runs fine with no problem, it's just weird
to see the temp gauge behave like that.

Thank you.


Martin