Why/How would tunring on A/C cause overheating?

[ripnbst]

So my car before it overheated would heat up REAL quick with the A/C on. Why? Can anyone explain to me why my car would overheat when I turned the A/C on? I was on my way somewhere sitting in stop-n-go traffic and I noticed the temp started going up so I turned it off and didnt rise any higher. Then the other day I was on my way home from work on the highway doing 70mph and I had the radio on and was in traffic and wasnt looking and the car overheated and now my motor is totally fucked. I ahve thought about it and I dont have a great understanding of the A/C system and how it works, someone help me out here. Another question, why didnt my CEL come on? It works, when I turned the ignition to ON it would light up adn then go out when I started the car. Never lit up when my car was hot enough to cook eggs on. WTF Nissan Engineers?

[Mathetai]

The AC works off a belt which is run by the main crank pully. This causes more power to power to be put on you engine (thats why the RPM's are higher with AC on). I had an old supra that had the same problem. GL mang! :)

[mmeedd26]

You need to bleed the air out of your colant lines.... When the air pockect hits the engine over heats and temp will shoot up A/C will blow hot air... when the pocket passes then everything is normal....

Happened to me some years back and I was like WTF because for no reason my car would get hot..id pull over start it up wait then it would be ok....

Took it in and the mechanic said..... the coolant lines had air in them.. So if coolant was added and it wasnt bled properly you will have issues...

Check that out. Sounds like your problem.

[ripnbst]

Well its too late now, my motor is already junk. But thanks for the input.

[BoostedCoupe]

to help it from overheating the e fan comes on. but yes the reasson is cause of more strain put on the motor.

[motonagam]

another reason is because the radiator doesn't receive the full cool air when it goes through the fins because incoming air has been preheated by the A/C condenser before hitting the radiator when the A/C is on.