When an air conditioner makes a strange noise upon starting up after being off for a while, it can be attributed to a few possible causes:
Thermal expansion: Air conditioners contain various components, such as coils, pipes, and panels, which expand and contract as they heat up or cool down. When the air conditioner is off for an extended period, these components reach room temperature. Upon startup, when the system rapidly heats up or cools down, these components undergo thermal expansion, which can result in clicking, popping, or creaking noises. These sounds are generally harmless and occur as the materials adjust to temperature changes.
Lubrication issues: Air conditioner compressors and fan motors have bearings that require lubrication to function smoothly. If the system has been inactive for a while, the lubricant may settle or dry out, leading to increased friction and noise during startup. As the air conditioner runs, the lubricant redistributes, and the noise may diminish. Regular maintenance, including lubrication of moving parts, can help mitigate this issue.
Loose or worn-out components: Over time, the vibrations and regular operation of an air conditioner can cause various components to loosen or wear out. When the system starts up after a period of inactivity, these loose or worn-out parts may create rattling, vibrating, or banging noises. Common culprits include loose fan blades, motor mounts, or loose panels. Tightening or replacing these components during routine maintenance can alleviate the noise issue.
Belt problems: In older air conditioning systems, a belt connects the motor to the blower fan. If the belt becomes loose, worn, or misaligned, it can produce a squealing or screeching noise when the system starts up. Adjusting or replacing the belt as necessary can resolve this problem.
Debris or obstructions: Foreign objects, such as leaves, twigs, or debris, may accumulate in the outdoor unit of the air conditioner during periods of inactivity. When the system starts, the fan may encounter these obstructions, resulting in a buzzing, rattling, or grinding noise. Regularly inspecting and cleaning the outdoor unit can help prevent this issue.
If you consistently experience strange or loud noises when starting your air conditioner, it is advisable to have it inspected by a qualified HVAC technician. They can diagnose the specific cause of the noise and address any underlying issues to ensure the proper functioning and longevity of your air conditioning system.