The engine over heat unless air conditioning is on

The warning lights are probably not related to no heat, unless the engine is low on coolant.
It sounds like a problem with the blend doors under the dash, or the main controller. You may need a shop manual to diagnose it.

your car should have two cooling fans,one is for the engine radiator and the other for the air conditioning.The engine is getting overheated when air conditioning is on I strongly believe the fan for the a/c is not working.The other reason is the air condition does not have enough freon , Top up the ac and follow it .

The air conditioning condenser creates a lot of heat when the a/c is on. The cooling fan is supposed to run the whole time the a/c is on to keep it cool. If the fan isn't on, the radiator will absorb this heat and cause your car to over heat. You should also check your coolant level. So, it sounds to me like your cooling fan isn't working.

over heating

whats the fuse for. if it operate the air conditioning system on the engine fuse box ur compressor clutch is burnt. if its the fuse inside the car it o\powers the hvac controls. put a new fuse on unplug ur compressor clutch connector and turn the engine on switch your air conditioning and heating controls on and off see if it blows the fuse again if it does then u have a problem with ur inside wiring circuit or heating ventilation air conditioning controls. good luck.

There is a blend door problem.

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HEATING AND AIR CONDITIONING Refer to Section 1 for discharging and charging of the air conditioning system. The heating system provides heating, ventilation and defrosting for the windshield and side windows. The heater core is a heat exchanger supplied with coolant from the engine cooling system. Temperature is controlled by the temperature valve which moves an air door that directs air flow through the heater core for more heat or bypasses the heater core for less heat. Vacuum actuators control the mode doors which direct air flow to the outlet ducts. The mode selector on the control panel directs engine vacuum to the actuators. The position of the mode doors determines whether air flows from the floor, panel, defrost or panel and defrost ducts (bi-level mode).

Heater Core CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old HEATING AND AIR CONDITIONING Vehicle air conditioning is the cooling r refrigeration of the air in the passenger compartment. Refrigeration I accomplished by making practical use of the laws of nature. HEAT GOES TO LESS HEAT. All this means is that heat transfers. If two substances of different temperature are placed near each other, the heat in the warmer substance will always travel to the colder substance until both are of equal temperature. As a fail-safe, the air handling system is designed to provide defrost when no vacuum is applied to any of the vacuum control motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak. Instead, a leak in the vacuum control circuit will send all airflow to the defroster outlets. This condition may occur during acceleration (slow vacuum leak), may exist at all times (large vacuum leak), and may happen only when certain specific functions are selected, indicating a leak in that portion of the circuit.
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That is all that is listed for Heater Core on my online resource. Sorry that it is not more explicit for instructions.

Maybe try Alldata.com for more information, but it will cost.

You need review details in the Service Section-24-Heating-Air-Conditioning and Section-24a-Heating-Air-Conditioning

Hope helped with this. Good luck.

At the radiator, drain and then flush with water then add 1 gallon of new antifreeze and top off with cool water. Now the cooling system will work.
If you have not performed routine maintenance on your cooling system - it will clog the heater in 10 years or less. Sometimes a bottle of radiator flush (purchased at any walmart or kmart) can clear the heater core - but you will have to run it with the heater on full heat setting for a few hours of driving.

Let us know!!

Unless you mistyped, you are talking about two different things.

Coolant and topping it off, has nothing to do with your AC. Coolant is what keeps your engine from overheating.

Your AC probably needs to be recharged and checked for leaks. Bring the car to an AC shop and they should be able to help you out.

If your AC checks out fine, I'd start by looking under the dash. There's a possibility that the flap that moves when you switch from heat to cool is stuck in the heat position.