Your home or business heating, ventilation and air conditioning system, or HVAC, relies on a motor to blow air throughout the building. While these motors are generally dependable, the internal parts that create friction do eventually wear out. If the motor won't start, go through this checklist to determine if it's a simple problem you can fix or if it's time to call a repair shop.
On/Off Switch and Circuit Breaker
There is an on/off switch on the HVAC unit in addition to the building circuit breaker. Make sure both are turned on. If the circuit breaker has been tripped and you reset it, watch it for a few minutes to make sure it doesn't trip again. If it does, leave the unit turned off and call for repair.
Any of several problems could be the cause of a repeatedly thrown circuit breaker. For example, the air conditioning compressor could be seized or the motor could have a bare wire shorting out the unit. Don't worry, you can usually avoid the expense of buying a new motor by sending it to a repair shop.
If you have advanced handyman skills, you could remove the motor and take it to the shop. Otherwise, don't mess with it. Call a company like Hackworth Electric Motors Inc. Most shops will send an electrician to your home or business to verify your diagnosis and retrieve the unit. Sometimes they are able to make repairs on the spot especially if the motor does not need to be rebuilt.
When the motor runs fine for awhile but then suddenly shuts off, the problem might be thermal overload. This usually happens when there is too much friction between the moving parts of the motor. A special machine oil lubricates the moving parts to prevent the motor from overheating. Today's motors are sealed units that do not need additional lubrication. Sometimes the seal leaks, however, and the lubricant flows out. The result is thermal overload.
Defective Motor Control Switch
HVAC systems have a switch, known as the electric motor control, that automatically turns the motor on or off as needed. Sometimes the motor is fine but the control switch is the problem. If electricity is passing through the system to the motor but the motor is not starting, then the control switch is the likely culprit.
Worn Mechanical Parts
Any object subjected to repeated friction will eventually wear down. For example, jagged rocks in a river are eventually worn smooth from the constant friction of water passing over them. The same thing happens to electric motors.
The first thing the repair tech will test is the motor shaft. If they are not able to turn it, they will look for an obstruction. If there isn't any, the problem is with the bearings. If they are able to turn the shaft, the problem is most likely with the fan.
There are several other reasons for a motor to not start or to shut down prematurely, such as a loose motor mount or shorted windings. When the problem is with the motor, choose a shop that is certified for electric motor repair to ensure the work is done correctly. After all, your HVAC system is a major investment.