You need to check the fan clutch. If it kicks in and roars, it's too hot and it's slipping.

 

When you have a good fan clutch, as the temp rises, the fan will spin faster and the temp will cool down, this process should be somewhat invisible to the driver. The engine will run slightly warmer in higher ambient temperatures. If your A/C warms up at idle, you do not have enough air flow through the condenser.

And I agree, the condenser and radiator fins get plugged over time, the amount of time depends on your driving environment.

First clean the outside of the condenser/radiator if no improvement, then clean the inside of the radiator, if no improvement, then replace the fan clutch.

 

I had this same issue in my 2000 chevy blazer, had to drive home with my temp getting up to 260º. i had recently replaced my water pump so i knew that wasnt the issue. seemed like there was lack of flow in my water system, so i replaced my thermostat to make sure it wasnt sticking. next i installed a new radiator. fixed it perfectly, found one for about $130. havnt had an issue since.

 

Thanks for all the responces. I should expand and say that the radiator was cleaned inside and out. and when I say that the airconditioner blows hot air at idle is because the compressor kicks off and kicks back on again but stays off more then it comes on, but only when the temperature reaches 200 + I dont know why the compressor does this when the temp is hot.

 

If there is not enough air flow, the Compressor will build up high pressure and turn off until the pressure goes down. If it doesn't do this while moving it's the fan clutch. You need to watch it with A/C gauges.

If the problem is not as bad while moving, then your air flow through the condenser/radiator is blocked somehow.

Of course if the A/C is not charged properly, or has air or moisture in the system, it could behave this way too.

I would start with checking pressures, then check airflow blockage, if those are good it's probably fan clutch. The fan should roar when temps climb.

 

Ok I will do this Thanks. I will let you know what I find out.

 

Actually I got my Blazer to 190 degrees and reved the engine up and shut it off immediately and the fan spun for 3 seconds more. It is the fan clutch im sure from this.