If you have an electric furnace some causes of circuit board failure may include the following.
Furnace control board problems.
Interruption of the regular sequence of events.
When an electro mechanical switch like the ones on our boards is suddenly being used after a long period of downtime like the end of one winter to start of the next winter it can become permanently stuck.
Tapping on the relay can sometimes help but only delays the inevitable failure of the board.
If the furnace s draft inducer will not start or if the blower motor will not start then this could very well be a control board problem.
It is hot and they need air conditioning now.
Debris and dust can cause the air filters to clog.
Here are signs you may have a malfunctioning furnace control board.
It is on the weekend when getting a control board is impossible or the person does not want to wait on a new control board to be shipped in before they can use their air conditioner.
The problem is that the blower fan will not come on because the fan relay on the control board has failed.
After a certain period of time the furnace wires will become loose due to the vibration.