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<div id="post_message_">I'm
trying to figure out why my radiator fans dont turn on when my engine
becomes hot but turn on when i turn on my ac. I have a wire running to
a manual switch and positive battery cable and the light blue wire on
the fan. Also i have a 95 buick lesabre. If i change out the coolant
temp sensor will that make my fans turn on when the engine gets hot?
also when i turn on the ac the check engine light will come on saying
p1640 - qdm 1 failure &amp; p1650 - qdm 2 failure.</div>