If your furnace turns on and then turns off before your home has had a chance to heat up properly, the problem might be with the control board. A few things can cause this problem, so a heating repair technician should check the parts to see which one is malfunctioning. If the control board is bad, it will probably need to be replaced rather than repaired. Here's how the control board is supposed to work, the signs that it's bad, and how a bad board is replaced.

How A Furnace Control Board Works

A control board looks similar to a motherboard in a computer, and it has a lot of wires connected to it. These wires go to all the parts in your furnace that work in sequence to turn your furnace on and off. The thermostat triggers the board to start the parts one after the other that bring your furnace to life and then shut it down when the correct temperature is reached.

Why A Control Board Goes Bad

Small parts on the board can wear out over time. This can happen due to expansion and contraction of the metal, a power issue, worn wiring, or even water dripping on the board. If the board goes bad, your furnace may not start up at all or it may not shut off. The furnace may partially start and then shut down. The control board has indicator lights on it that lets you know the point at which the starting of your furnace failed.

How A Bad Board Is Replaced

If the heating repair technician verifies the control board is bad, they'll replace it with an exact duplicate. A control board looks difficult to replace since it has so many wires going to it, but the job isn't too difficult as long as the wires don't get mixed up.

The first step is to shut off the power and then remove the panels on the furnace to expose the board. A good way to keep track of where all the wires go is to take them off of the old board one at a time and move them to the new board even though the new board isn't installed yet. By doing this, the heating repair contractor keeps track of all the wires and makes sure they get in the right place on the new control board.

When all of the wires are removed from the old control board, the board can be taken off of the mounting plate. The new board can then be mounted to the plate by pushing it in place, and since all the wires are attached already, all that's left is to test the furnace to make sure it functions properly.