If the air conditioner in your Honda Civic is not producing cold air, the air conditioner's compressor could be the problem. This part of the system is essentially a pump that compresses the refrigerant into a high-pressure gas and sends it through the system. Environmental laws require at least the partial assistance of a professional to change this part if needed.
Take the car to have the air conditioning system discharged. This must be done by a licensed professional at either the dealer maintenance department or another air conditioner repair shop.
Disconnect the battery's negative cable. Raise the Civic's front end, support it on jack stands and remove the left front wheel. Make sure the parking brake is applied and block the rear wheels with large blocks if you can.
Remove the power steering and air conditioning compressor drive belts by loosening the mounting bolts and locknuts with a ratchet. Remove the alternator by loosening the lock bolt and adjusting bolt from the bracket between the alternator and compressor and then the upper alternator mounting bolt. Remove the splash shield from beneath the engine compartment.
Remove the condenser fan by removing the two bolts at the top of the fan and pulling the fan out of the compartment.
Disconnect the wiring harness to the compressor clutch. Disconnect the refrigerant lines from the compressor by pressing the tabs on their quick-connect fittings.
Unbolt all of the mounting bolts to the compressor using a socket wrench. Guide the compressor carefully out of the engine compartment through the opening at the bottom.
Transfer the clutch from the old compressor to the new one if needed. You will likely need a special tool from an auto parts store to remove the fasteners to the clutch.
Add refrigerant oil to the new compressor. To figure out the amount you need, drain the oil from the old compressor through the suction fitting, measure it and subtract the amount from 123gr to get the correct amount.
Install the compressor in place and attach the mounting bolts. Connect the electrical connector and refrigerant lines, using new O-rings where the line fittings connect to the compressor.
Re-install all the engine components in the reverse order of removal. Make sure the drive belt is routed in the same path that it was before.
Lower the car, reconnect the battery cable and take the car back to the shop to have the air conditioning system evacuated and recharged.