2000 grand prix, temperature won go from ac to heat, stuck on ac.

Question edited for clarity.
Question moved from Home Heating and Cooling.
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What is the difference between Pontiac Grand Am and Grand Prix?

The main difference between the Grand Prix and Grand Am is that the Grand Prix has a plain body and automobile AC system. On the other hand, Gand am is a curved-bodied and manual AC featured vehicle. Both the automobiles have amazing features and are different from each other in several aspects.

The parts you mentioned should be fine.

https://www.google.com/search?q=2000+Pontiac+Grand+Prix+v+1996+Pontiac+Grand+AM

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i would change the thermostat and coolant temperature sensor, this sensor tells the fans when to come on and turn off, hope this helps

Sounds like the fan thermostat is not working. If the fan doesn't come on then it will overheat when there is no airflow. When you drive it the air flows through it just fine.

The outside air temperature is reading sometimes off then the ac does not work? The ambient air temperature sensor located right by the front grill is probably malfunctioning.If it reads below a certain temp it sees no reason to turn the air on so it doesn't let you.

the temperature sending unit on a 97 grand prix 3800 gt(which is also the coolant temperature sensor) is not accurate. the sending unit part of this sensor only sends info to the guage on the dash. the coolant sensor part sends info to the computer of the car. it is located under thermostat and somewhat difficult to get at. i had put a brand new one in and my temperature on my dash is all over the place---even with good thermostat and properly bled system. when i hook up a scanner to my computer, the coolant sensor is sending the computer(ecu??) what seems to be the right temp. anywhere from 194 degrees to 217 when hot. the guage however on dash go from 160 to 260 in less than 2 minutes.

orfice tube stoped up or make shure motor electric fan comes on when u cut ur ac on with motor runing

i have been having that same exact problem with my 2002 grand prix for over a year now, and when my ac is on the lower setting the it doesnt work plus the headlights and lights on my dash go out. On Max everything works. i changed the blower resistor(about $35), still doesnt work. i changed all relays and fuses related to the ac, still doesnt work. i changed out the actual ac control switch in the dash, still doesnt work. i have changed everything but the blower motor and have asked every mechanic and auto parts retailer i come across and no one knows the answer. The best answer i got is that it is probably a wiring problem like a short somewhere.

change the sending unit to the fan, if that doesnt work check for power too the fan or even a bad fan

check your wiring harness where it hugs the engine on the right front side, because of vibration this area is prone to broken and shorted wires

Check the relay for the blower. it may be locked . tap it lightly or jiggle the relay or check with a known good relay.this two circuits may be interconnected. check the light relays as well and fuses.