AC units will sometimes blow warm air if there is a problem with the electrical system. There are various fuses, pressure switches, and relays that will wear out and the AC unit is designed to not operate if it detects that there is a problem with any of these components. 

Rule Out Other Causes First

Before you begin searching for electrical problems that are causing your AC issues, you should first look for other causes. For example, there may be a refrigerant leak. Recharging the AC with more refrigerant will temporarily solve the problem, but the leak will eventually need to be repaired. It is also important to check the compressor to make sure that it engages when you turn on the AC. Make sure that there is no obstruction in the orifice tube. Also, make sure that the blend air door is not stuck in the heat position. 

Faulty Sensors

There are several sensors in the AC unit that make sure that the AC does not have too much pressure or does not overheat. If the sensors detect a problem, they may cause the AC unit to shut down. The sensors may also become defective and will need to be replaced.

A Faulty Actuator Or Blown Fuse

Depending on the car model, the AC door might be controlled by an actuator. If the actuator becomes defective, it will need to be replaced. Also, the problem may be the result of the blower not functioning properly. There are several electrical components that direct electricity from your car's battery to the blower. Two fuses affect the blower motor. One fuse is in the engine bay box and the other fuse is in the under dash fuse box. If you can locate and replace these fuses, you may be able to get the blower to function properly. If both of these fuses are working properly, there may be a problem with the:

  • Relays
  • Pressure switches
  • Another fuse

When the faulty component is detected, it must be replaced so that the AC unit can operate without damage to the system. 

Repairing the electrical components of the AC unit can be difficult unless you have the right equipment. For this reason, it is recommended that you hire an auto repair technician specialized in AC units. It is also difficult to test the AC unit without the proper experience. Check places like Modern Auto Air for more information.