It sounds like your cooling is not working when you turn on the a/c system...........
The cooling system in your car (radiator) cycles fluid (water with anifreeze/coolant) through your engine to keep it from overheating. It carries heat away from the engine.
IF IT WAS NOT OVERHEATING BEFORE THE HOSE WAS REPLACED -- MORE THAN LIKELY YOU HAVE AIR POCKETS TRAPPED IN YOUR COOLING SYSTEM
One of the major causes of a car overheating is a leak in the cooling system. Other causes are a clogged radiator, a bad thermostat, a broken or split hose, a worn out water pump, and a faulty cooling fan.
Check the coolant level, the cooling system hoses and the radiator, if it's fine you need to check the thermostat.
NO!Do not ever put anything into the engine's cooling system that wasn't designed for a car.
every 5 years or 100,000 miles you can flush the cooling system , drain the system firset , fill with water , add the flush and let the car run until it reaches normal operating temp ( 180-210) , let the car cool down and then drain the water and the flush liquid out , fill up the radiator with the new coolant , a 50/50 mix , make sure you let all the air out , there should be air breathing points that you can let loose till all air is out
Air not properly purged out of the cooling system, bad electric cooling fan switch(s) in the block, bad connections on the block fan switches.
If there is no cooling system, the engin will overheat.
If you are talking about the low coolant light then it is just low of coolant. If you are talking about the coolant temperature light, then the engine is overheating. This car is 7 years old. Have the cooling system serviced. Drain the coolant and flush the system. Install a new thermostat, and add a 50/50 mix of antifreeze and distilled water.
Check your owner's manual. The symptoms you describe sound like those that indicate that the "Fail Safe Cooling System" is being activated by high engine temp. Check your coolant level AND make sure the water pump hasn't failed.
It is heated to such a high temperature by going over the engine which is really hot and is part of the cooling system, the cold air goes over some part of the engine and comes out hot. It is part of the cooling system of a car, so therefor if your car has overheating problems turn the heater on.