Mitsubishi Repair: Engine stall and air conditioning, advanced auto parts, excessive tension

Question
Have a 2001 Galant ---- there's something going on with my air conditioning that is making my engine stall out.  I can turn on the blower switch without a problem but when I push the switch knob in to turn the air conditioner on I hear the relay ( I guess) clicking and then the engine stalls.  Also noticed that the led that is supposed to light up on the knob when the air is turned on ... doesn't light up.  Engine isn't stalling (so far) if the air is left off.  

Any help you can give me is very much appreciated.  

Answer
J,
When your A/C is running, that puts an extra strain on your engine, which in turn puts an extra strain on your alternator.  If your alternator is malfunctioning, it will not supply enough current to fire your spark plugs, and that can cause your engine to stall.  The first thing you should do is have your alternator checked.  Most auto parts stores like AutoZone and Advanced Auto parts can check your alternator for free.  It may also be a good idea to check your spark plugs and replace them if they look worn.

Excessive tension on the A/C belt can also cause the alternator to run slower, therefore causing the problem I mentioned above.  Another possibility is a malfunctioning Idle Air Control (IAC) motor.  That motor is responsible for allowing more air into your engine when an extra load is applied to your engine; like from your A/C.  If the IAC is not functioning, your idle speed will drop signifigantly when a load is applied, and your car will stall.  Have the IAC checked if the items I mentioned above do not remedy your problem.  Depending on when you bought your car and the number of miles on it, some of these items may still be covered under your warranty.
Good luck!