Pontiac Repair: fluctuating temp gauge into the red but not overheating, blown head gasket, coolant level

Question
1994 pontiac grand prix - car had a coolant leak(don't know where) and after it was fixed, the temp gauge goes up into the red and hot light comes on.  Car has been to  two mechanics 7 times.  It is not overheating.  Heater blows cold air half the time.  AC works good until the gauge rises up into the red zone. then it warms up.  second mechanic thought he had it and changed the 2'pigtails' to the gauge and sensors to one 'pigtail' to whichever one is in the front.  He had found a fix on the internet for Baretta's but problem sounded similar to my pontiac. Didn't work.   Temp gauge just drifts from 100 to over 200.  thermostat has been changed, tested car for cracked block, changed rad. cap/Pushing the ac button will usually bring the gauge back down out of the red.

Answer

Your car IS overheating!!!!!

That is why you loose your heat and why the AC starts to blow warm.

I am very aware of the fix on Baretta's but it is not the same set up as your car. Normal operating temp on your car is about 220 degrees and the fan will come on at 229.
The most common cause is a blown head gasket.
But 1st, check the coolant level and check for proper fan operation. The fan should turn on when the AC is turned on or when the coolant reaches 229 degrees.