You operate your furnace all throughout the cold Illinois winters to keep your home warm, so the unit really does work hard. In the event the unit stops working altogether, you likely know all the usual suspects that can be to blame, such as the breaker panel or power supply. However, there can also be some often-forgotten reasons a furnace will not power on. Take a look at some of these causes so you are better equipped to handle a dysfunctioning furnace when it occurs.
The safety switch is on because the access door is open or removed.
If you have recently cleaned your furnace or had maintenance performed and the thing refuses to come on, there is most likely a logical solution. Furnaces have an access door that has a safety switch that has to be turned off before you can even pull the door open. This feature prevents anyone from getting inside of the furnace while it is in operation. Therefore, if your access door has recently been opened or removed, there is a chance the safety switch is still tripped and your furnace is not going to come on until the switch is back in operating position.
The furnaces blower unit is locked up.
If you have an older furnace with a blower system and your furnace will not come on, what you could be experiencing is a problem with the blower and not the actual furnace. A lot of the furnaces out there are designed to not come on if there is a malfunction with the blower unit. The reasoning behind this feature is so that extruded heat does not accumulate inside of the furnace and cause overheating. It is not uncommon for older blower units to lock up because the motor has worn out, in which case you will have to have the blower replaced by a professional.
The flame sensor is dirty.
If you have a gas furnace with a pilot light, behind that pilot light will be a rod-shaped mechanism that actually acts as a sensor. The job of this sensor is to let the furnace know it is safe to come on, so if the thing is caked with year's worth of dust and debris, your furnace likely will not come on at all. Cut the power and gas supply to your furnace and use a dampened rag to carefully clean off this sensor if you suspect it is causing the problem.
For more information, get in touch with a furnace repair contractor.