The climate control may not work right, if i want heat, it blows cold air although the temp gauge shows hot on the engine then cold...

warmth comes from the heater in the car
if it is climate control check the climate control module
check for heater control in the vent settings as the hot water tap may not be turning on

If you are getting hot water/coolant to the heater core and still no hot air coming out the vents, then it's a issue with the climate control or blend door. After running your engine and it reaching normal operating temp, locate your heater hoses that goes to the heater core. Carefully touch them to make sure both hoses are hot to the touch, if they are, you are getting hot water/coolant to and from the heater core. So, then it will have to be a issue with the climate control in the dash or either the blend door in the air box. It's a common problem for the climate control to go out on these models, hope this helps.

Could be air in the cooling system , try an bleed the system . On top of the thermostat housing is a bleeder valve , with the engine up to temp. open valve till coolant comes out . Is the coolant full ? What color is the coolant ? Have see where coolant turns like a muddy color an clogges the heater core an engine coolant passages . Check the heater hoses going into the fire wall ,are they hot ? Does your grand prix have manual or automatic climate control ? Duel zone ! Do you hear a clicking sound behind the instrument panel ? Bad temp blend auctuator .

It sounds like the system is fried. Based on the description, it is just pulling in the outside air and not doing anything to heat or cool the flow. Unfortunately, this is a job for your preferred mechanic.

Always check body grounds. You may have good power to the engine with a good ground still, but your body grounds control power to all else.

I have a 2000 pontiac grand prix with a digital climate control system. The heat quit working, it doesn't blow out any heat. Now that it is warm outside the air stopped blowing out any air. The digital temperature on the climate control is not correct. When it states that it is below 30 degrees on the ext and it is warm outside the air wont be cold. Once it starts going above 30 degrees the air gets colder. Today the blower stop working all together. Was told it maybe the climate control unit was bad. You can hear the door opening/shutting when you switch the temp from cold to hot. But there was no heat blowing out whatsoever in the winter time. Could you please give me your opinion on whether or not it is the climate control unit or something else?

if your vehicle has the electronic climate control, it is probably the blend door motor/actuator that has failed and is stuck at the temp that was last entered in the climate control unit when it failed. this can be a very time consuming repair to do as it is under the dash. the other possibility is your coolant level is low and not allowing the heater core to bring the outside air up to the temp you want. if that is the case,your low coolant temp sensor should have come on. if not, then the thermostat could be either stuck open or closed. if stuck open the engine would not always show the temp gauge at normal operating temp of 195-200 degrees. if stuck closed the engine should be overheating according to the temp gauge. you did not mention what the operating coolant temp was!

I think you could be right about there being air trapped in the system.
Or the heater core(radiator) is plugged.
Either way you need a pressurized radiator coolant pump to put the coolant in without air being trapped.
Although,i have seen it done by jacking the vehicle up high enough that the radiator was now higher than the heater core level, and then the coolant was put in.
But this is dangerous to try.

Check to make sure your thermostat works right by monitoring the warming up of your engine. With a completely cold engine, start and run the engine for a few minutes, then put your hand on the top radiator hose to monitor if and when it gets warm as the thermostat opens more and more and note the gauge reading( if it works) the top radiator hose should be unbearably hot within 5-8 minutes. If the therm. opens right it should close right aswell, staying open a little while eventhough the radiator may have cooled may be what you are experiencing causing the rapid cooling and is nothing to worry about. The Hose should not get warm very soon after starting the engine. Regarding you gauge, lets take one step at a time, verify proper op. or the therm.

Temp. actuator stuck on heat , probably . Manual or automatic climate control . Electrically controlled temp actuator , or the door is stuck in heat side.