Updating Your HVAC Unit

Why Your Blower Fan Won't Start

The blower fan is an integral part of the air conditioner (AC) — the fan pushes the air so it can circulate and cool the house. That means a malfunctioning blower fan will leave your house uncomfortably hot. Below are some of the reasons you might be in such a situation.

Control Problems

The AC relies on a series of controls to start and continue cooling the house. For example, the thermostat detects the ambient temperature and sends the signals to the electronic control board. The electronic control board controls various parts of the AC — for example, it triggers the cooling cycle.

A malfunction to any of these controls can interfere with the operations of the blower fan. For example, a thermostat with disconnected wires won't send temperature signals to the electronic control board.

No Electrical Power

The blower fan needs electricity to run. The electrical power runs the blower motor, which runs the fan. Thus, any problem that cuts off electrical power to the blower motor will prevent the fan from running. Examples of such problems include a tripped circuit breaker, power blackout, corroded electrical contacts, and an off switch.

Blower Assembly Issues

Malfunctions in the blower assembly can also lead to the blower fan not running. Here are examples of such issues:

  • A loose fan belt
  • A broken fan belt
  • Loose pulley (for belt-driven blower assemblies)
  • Damaged assembly bearings

In short, anything that interferes with the operations of the blower assembly can interfere with the fan's operations too.

Bad Capacitor

A capacitor is an electronic device that stores electrical charges. Most residential ACs have two capacitors: a start capacitor and a run capacitor. The start capacitor provides an electrical boost to get the blower motor running. The run capacitor provides the electrical boost to keep the motor going once it starts running. A dead-start capacitor means the blower motor won't start.

Motor Issues

The blower motor is just like any other electrical motor — the motor turns electrical power into kinetic energy. A dead motor won't run, meaning the blower fan won't turn if the motor has failed or is dead. Overheating, corrosion, and physical damage are all possible causes of motor failure. Such things can damage the insulation on the wires that form the motor windings, leading to an electrical short-circuit.

You might not know what ails your blower fan without a professional diagnosis. Consult an air conditioning repair technician to diagnose the problem and save you from the discomfort.