This is a photo I took of a recent call I was on in which the customer Dan had no heat and was himself a DIY guy. Even still, he couldn’t figure out what was going on. He had checked power to the furnace, checked the little light on the control board, the unit didn’t seem to be doing much at all but he stated that he smelled gas. After looking at what the unit was doing through our facetime call, it was determined that the hot surface igniter was bad. He was forever grateful for my service and we were able to get him the part he needed and got him up and running for under $100.
Hot surface igniters come in many shapes, sizes and types so are sure to order the one matched to your furnace make and model. There are also universal styles as well which may work if you are in a pinch. In order to get this igniter to work, there are a series of events that must happen. The first is a signal is sent from the thermostat to the control board, the control board passes 24 volts from the transformer to a series of safeties including one or more rollout switches and one or more limit switches. Then the inducer motor starts and closes one or more pressure switches. Once the power passes through all of these safeties, it then sends power to the igniter which will glow bright orange as shown in the photo above for a predetermined period of time, usually 5 to 10 seconds. After this, the gas valve will be sent power, open up and you’ve got heat! Use caution when handling these hot surface igniters and be sure to never touch the surface of them. They are very fragile and the oil from your fingers can cause the igniter to fail prematurely. (photo of failed hot surface igniter below)
As always, if you need any help determining your equipment’s correct replacement igniter or trouble-shooting a bad igniter, you can use our VIRTUAL DIAGNOSTIC tool or instant messenger and let our expert technicians at Fixmyfurnace.com help you out.