It’s December and the temperature is dropping, or at least it should be. Needless to say, the bulk of our service calls are for no heat situations. In talking to our service technicians one of the biggest reasons for these heat failures is worn out parts. Things like ignitors and blower motors are finally giving out after years of service.
Hot surface ignitors do the job that pilot lights once did. They are made of a highly resistive material that uses electricity to become red hot. Once the ignitor has had sufficient heat up time, generally less than 30 seconds, gas from the burners is introduced and ignited by the red hot material. The resistive material the ignitor is made from becomes weak over time and eventually will fail. Usually they develop a crack, but not always. The current passing through the ignitor can be measured with a meter, and if the ignitor becomes too weak they will not pass enough current to adequately heat up and ignite the gas. So even though the ignitor appears to be working, it won’t ignite the gas. Many manufacturers provide information in regards to minimum currents necessary to provide reliable ignition every time. If the current falls below the minimum they will eventually fail to ignite and cause the heating system to go into a safety lockout. If the information for your particular unit is available, a service technician can measure and determine if the ignitor is becoming weak and needs to be replaced during a preseason checkup.
The blower is what pushes the heated air through the ducts of your building. Blower motors run off and on all during the heating and cooling seasons. They work the hardest when they first start. All of that off and on running eventually takes its toll on the motors. A motor can be working fine one day and be dead the next.