Before we begin analyzing your systems issue, its important to make sure that your HVAC system is well maintained throughout the year. Alternating seasons can put your system through a lot! The best way to keep your system working efficiently all year long is to have it serviced once every season.
You might notice the following issues with your system when you start it:
A buzzing noise is coming out of your outside unit
Leaves or debris made its way inside your system. The blade fan inside the unit might have come loose. Your condenser coil might need to be cleaned. Some of the lines inside the unit are rubbing together and causing a noise.
Your system is screeching
When your system turns on you can hear a constant screeching noise emitting from the unit. Typically this is an indication that your fan motor is going to fail. The cause is bad bearing inside the motor.
You can hear loud slam
If your system makes a loud slamming noise when its turning on or shutting off the springs inside your compressor have failed. The compressor wobbles as the system shuts off and slams against the casing.
You can hear loud bang
If you hear a loud banging sound while your system is running, most likely a part of your condenser fan has come loose and is banging against the case as the fan spins.
A whistling sound is coming out of your system
If your system turns on and you can hear a whistling sound for the first few minutes of operation, most likely your refrigerant pressure is too high and its causing a whistling sound as well as your system to turn on and off constantly.