Over Heat

Ok so I have a 2004 Mitsubishi Outlander Sport AWD. It has started to over heat only when stopped at a stop light and only when the A/C is on. It will red line and as soon as I start to drive the gauge will drop back to normal. Then as soon as I stop again it will red line. But when I turn the A/C off it will fall back down to 3/4 over heat and drop immedialtey as I start driving. I notice that the A/C will go from ice cold to blowing hot air when it starts to over heat. I took it to the shop and they did a pressure test on the cooling system and it didnt do it again and the shop said that they couldnt find anything wrong with the car. It didnt do it for about 2 weeks and just now it started back again!!!

use another shop. first one was not taking your symptoms serious enought. many more tests should have been run.

I agree with a second opinion here. Make sure that they check the coolant for air and for the proper level.

You may have corrosion in the cooling system. The blockage from the corrosion may have been moved when the pressure test was done, and now it is plugging the cooling system again. Have you ever had the coolant checked or changed on your car? I agree with @gdawgs. You should find another garage to test the system.

This Mitsubishi displays all the symptoms of radiator fan(s) that are not working effectively. Both fans should be running when stopped at idle and the A/C is ‘on’. The fans may not be pulling air efficiently or not coming on at all. This van has a control module for the fans so in addition to turning them ‘on’ the speed is probably controled by the module. The mechanic you use should be familiar with the sound of the fans running at high speed; able to read the RPM; and able to monitor the current flow. There are three (3) coolant temperature sensors involved here so check them for proper operatiion.