All newer furnaces are self diagnosing and will flash an led light in a sequence to give you a one or two digit trouble code . The code is usually published on the door of the furnace, service manual, or can be found online. Try to note the problem code on the furnace before any attempt to reset is made as it will help a professional if you can’t get it fixed yourself. It could be a number code or short and long flashes ie. 3 short 1 long would mean code 31

If the power is off on the furnace check that the power switch is turned on. The switch is located high on the wall or ceiling, It looks like a light switch and can be shut off by accident. Still no power then check the house breaker for the furnace as it sometimes will not fully flip instead just move a little. If breaking has tripped then the problem is short to ground in the furnace, Most times the problem will be in the motor.

One of the most common problems is a dirty filter so start by remove the furnace filter clean or replace as needed. Flat filters should be replaced every month, Pleated filters should be changed every 3 months. Pleated filters will last longer due to the larger surface area since if it was stretched out the filter would be three times as long. The type of filter I use needs the main box professionally installed but yearly changes can be done by home owner, just make sure you can buy the filters without dealer. the filter is about 5 inch wide and it only needs to be changed once a year.

Not every filter will last the specified time since every house is different and get dirty at different rates due to outside dust, inside rugs, animals.