The answer to 'how much to fix central air in Illinois' is that the cost to repair a central air conditioning system can vary widely depending on several factors. Generally, minor repairs like fixing a refrigerant leak or replacing a thermostat can range from $150 to $500, while more significant issues like compressor replacement can cost $1,000 to $3,000 or more.
The overall cost is influenced by the age and condition of the unit, the specific problem that needs to be addressed, the cost of labor and parts in your local area, and whether any additional work is required like ductwork modifications. It's essential to get quotes from multiple licensed HVAC contractors in your local area to get an accurate estimate for your specific situation.