What Causes Furnace Circuit Boards to Burn?

A furnace is designed to generate and give out heat, but it should not overheat itself. Although furnaces usually have a built-in mechanism to shut off in case this happens, you should recognize the likely causes and signs to deal with any issues before the situation becomes more serious.

Overheating is a sign that something may be wrong with the furnace that needs your attention. If your electric furnace is burning more than it should, there’s a good chance that the circuit board on the furnace is overheating.

Here are some possible causes of furnace circuit board burning and how to fix them.

In general, It could be due to restricted airflow so the vents might need clearing, the air filter might need replacing, or the blower fan or evaporator coil might need clearing. It also signifies something wrong if you hear strange noises or smells. Frequent sudden stoppages are another sign of a problem. It might be simply that you’ve set the thermostat too low, but it could also be a sign of a problem with the circuit board. In this case, your furnace may need to be repaired by a technician.

I will cover all the signs below.

Causes and Signs of Overheating

furnace vent

Restricted Air Flow

A common cause of furnace overheating is restricted airflow.

If the furnace does not get enough air for ventilation, it can cause overheating. This should be the first thing to consider when you notice the problem of overheating. Always check for the following:

Vents – The intake and outtake vents should be kept clean and clear of any objects. There should be no blockage in the ducts of any kind. If you notice any dust or debris accumulation in this area, this is likely to be the reason for the overheating. Never close any of these vents, either. They should always be kept open.

The first solution is to ensure both vents are open, clean, and clear.

Air Filter – The air filter is the appliances’ first line of defense to keep dust and debris out and maintain airflow. Dust and other debris can easily accumulate over time on the air filter. Therefore, it is important to check the air filter regularly (every few weeks or monthly) and change it frequently.

If you notice a lot of dust on the filter or it has worn out, replace it with a new one.

Blower Fan and Evaporator Coils – These are two more furnace components related to airflow that could cause the furnace to overheat. Usually, it is best to have them inspected at least once a year by a professional furnace technician. Otherwise, they can get damaged and become ineffective if they get too dirty.

Other Signs

Besides restricted airflow, there are other signs that the furnace has a problem.

Three other signs are:

Strange Noise – If you hear strange noises from inside the furnace, you should open it to check what is wrong. It might be a piece of debris, a loose or fallen screw, or something else, but it might also be a failing component. For example, a humming sound could mean the motor is overworking.

If it is confirmed that it comes from a component, you will need to have your furnace serviced by a technician.

Burning Smell – A burning smell is another sign that something is wrong. If the smell is persistent, stop using the furnace and have it checked.

Sudden Stoppages – If the furnace stops suddenly and frequently, either you’ve set a temperature on the thermostat that is too low, or there is something wrong with the furnace itself. It could be due to a failing component, a current overload, or the breaker may need replacing.

If it’s the breaker, you may be able to change that yourself, but if an internal component is a cause, then the furnace needs to be repaired.

Circuit Board Issues

circuit board

Here are some more causes of overheating, specifically originating in the circuit board:

  • Faulty starting capacitor
  • Dirty or wrong-size fuse
  • Loose wire
  • Thermostat control wire
  • Weakened blower motor

In all the above cases, if any component is faulty, it should be replaced. Some parts, such as the starting capacitor and fuse, are relatively inexpensive to do so. If the fuse happens to be too small, replace it with the larger one. Perhaps a wrong fuse was put in mistakenly during a recent repair?

If any parts are loose, such as the wiring, you must tighten them to guarantee good electrical contact.

Unidentified Causes

Suppose you are having difficulty identifying the exact cause, or there is still overheating, despite dealing with an issue you noticed. In that case, you can do one more thing before calling a technician.

Some electric furnaces come with diagnostic lights on their circuit board. Check your manual to find out if you’re unsure. If you have such a furnace, follow the troubleshooting instructions in the manual to interpret the light indications and fix the problem.

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About Sam Orlovsky

b1d87d2ee85af3e51479df87928bdc88?s=90&d=mm&r=gCertifications: B.E.E.
Education: University Of Denver - Electric Engineering
Lives In: Denver Colorado

Electrical engineering is my passion, and I’ve been in the industry for over 20 years. This gives me a unique ability to give you expert home improvement and DIY recommendations. I’m not only an electrician, but I also like machinery and anything to do with carpentry. One of my career paths started as a general handyman, so I also have a lot of experience with home improvement I love to share.

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