How To Test Your Furnace’s Ignition Control Module

What is an Ignition Control Module?

The Ignition Control Module (ICM) is a part of your furnace with one primary function: to light the burners. It receives a signal from the thermostat to start. It sparks (direct spark ignition) and sends power to the gas valve. It shuts down if the Ignition Control Module sensor doesn’t recognize a flame within a few seconds.

Unlike a fan board or full control circuit board, an ignition control module does not control the blower. It only controls lighting the burners. Because it uses an electronically-controlled ignition to light the burners, it is more energy efficient, generally safer, and more reliable than the standing pilot light found in most older gas furnace models.

However, ignition control modules can still encounter problems. Electronic ignition failure is quite common and can prevent your furnace from turning on.

Some furnaces utilize Intermittent Pilot (IP) systems, where the pilot only ignites the burner gas when the thermostat demands heat. Others use Hot Surface Ignitors (HSI), where electricity passes through a filament and heats up, eventually igniting the gas for the burner.

Could My Furnace Ignitor Be Bad?

Several things can happen when you have a faulty furnace ignition control module, but the obvious symptom is usually no heat. This is because heating doesn’t happen without furnace ignition. The ignitor must light the burners to produce warm air.

There may still be air coming out of the ducts; it just won’t be warm. This can be due to the circulator blower running as a safety measure when the furnace fails to light properly.

With an intermittent pilot system, your ignition may not spark at all, or the spark happens but does not light the pilot. Sometimes, the pilot will light, but the gas valve may not open, and the burner will not light. HSIs can also malfunction over time due to normal wear, damage due to improper handling, or a too-high electrical current in your home. Your furnace may start short cycling as the igniter attempts to light the furnace again and again. You may also notice the ignitor isn’t glowing red.

Troubleshooting Your Ignition Control Module

Many things can happen during the ignition process that can cause the system to fail. From failure to light the pilot to faulty sensors, any issue will signal to the circuit board that it isn’t safe to start the furnace. A few simple ways to investigate are:

  • Turn the furnace off, then wait a few minutes before turning it back on to see if the issue is resolved.
  • Check your furnace filter. A dirty filter can cause your furnace ignition to cycle on and off repeatedly, leading to malfunction.
  • Dirty filters, clogged ductwork, or plugged flue can cause limit switches to open when excessive heat buildup occurs.
  • Look at the ignition cable to ensure that there are no cracks or breaks and the connections are clean and secure.

How to Test for Basic Ignition Issues in the Furnace

To test your furnace’s ability to ignite, you’ll need a multimeter, but first, you must be sure you are taking all safety precautions.

  • Turn off all power to the furnace and close off the gas. Allow your furnace to cool before attempting any testing.
  • Remove the panel door and locate the Ignition Control Module (usually positioned near the gas port). If you see visible damage, then it needs to be replaced. If not, detach the wires, loosen the screw, and remove the Ignition Control Module from its socket.
  • To check if the ignition module is getting voltage, set the multimeter to AC voltage (VAC) reading and check for voltage at the thermostat input or 24VAC input to the Ignition Control Module. You should get a reading of 24VAC with respect to common or ground. If the multimeter stays at zero, a technician may be needed to troubleshoot the furnace for loss of power.
  • To check for ignitor resistance, set the multimeter to resistance readings (ohms). Remove the igniter from the circuit, connect the meter probes to the ignitor, and check the reading. A correctly functioning ignitor will give a resistance value between 40 – 200 ohms. If your ignitor has lower resistance, it’s probably ready to be replaced.

Replacement Ignition Control Modules

ICM Controls manufactures top-quality, cost-effective ignition control modules for gas and oil boilers, furnaces, and other heating appliances. Visit ICM’s website to cross-reference the part you need if you’re comfortable installing it yourself. If not, call an HVAC expert in your area.

surge protection for ev

Surge Protection for EV Charging

Low transient voltages

Transient Voltages at Low Levels: Why Should You Care?

protect devices from low transient voltages

What are Transients?

Known more familiarly as power spikes or surges, transient voltages are momentary changes in voltage or current that occur over a short period of time, usually lasting only fractions of a second.  But these “blips” can have a big impact.  In fact, transient activity is believed to account for around 80-percent of all electrically-related downtime. Transients can be oscillatory, where there are voltage swings above and below the normal line voltage, or impulse transients, where there’s one quick pulse above the normal line voltage—such as the case with a lightning strike.

Lightning is the transient source people usually think of first. Transients caused by lightning are seldom a direct hit, but rather a lightning strike near a power line that creates discharge. Normal utility operations can create transients as well during the switching of facility loads or capacitor banks, tap changing on transformers, poor or loose connections, high winds, even static electricity in very dry climates.

Transients can even be generated by the powering off and on of equipment in your home or business–photocopiers, laser printers, compressors, generators, and other motors, overloading a circuit, and defective wiring.

While high-intensity power surges are rare, most heavy-duty appliances like refrigerators and air conditioners create low-level surges every day. Although the damage may not be immediate, over time these minor surges can impact the general functionality, performance, and lifespan of that electrical equipment.

Read More: Power System Transient Studies using EMTP-RV

Why do we need protection from transients? 

The problem with transients is that they can negatively impact any connected electrical equipment and ultimately cause them to fail or work improperly.  Motors run hot, fail prematurely, and produce additional transients in the process.  Light bulbs run hotter, less efficiently, and fail early.  Black rings at the end of fluorescent tubes are a clear sign of transient activity. While replacing light bulbs may not seem like a major expense or inconvenience, replacing your HVAC system or new pool system certainly are.

For this reason, electricians recommend including surge protection as part of any HVAC or pool/spa installation along with a whole house surge protector.

Also Read: Prepare For Power Surges Says Electricity Providers

What is the potential benefit of a properly selected and installed SPD?

Don’t let transient power spikes get the best of you and cost you thousands of dollars. Today’s surge protectors can mitigate both high-amplitude transient voltages and the ever present low-level transient voltages. The most effective solution is a whole house surge protector that protects the circuits directly at the electrical panel. A whole house surge protector will help protect your electronics from internal and external power surges and can double or triple the life of electrical and electronic equipment.

Protecting your entire home with a properly installed surge protection device can:

  • Prevent damage to your electronic devices
  • Prevent high-intensity power surges which can cause destructive fires by regulating the passage of surplus voltage
  • Protect devices from the internal power surges which happen daily, prolonging their lifespan
  • Save you the cost of replacing expensive equipment that becomes damaged by transients. Whole house surge protectors are a cost-effective solution.

No matter how good, surge protectors don’t last forever, particularly with high surge activity, and may need to be replaced periodically. Look for a protector that has some way of alerting you that it has failed (usually referred to as “fault identification”), such as an indicator light or audible alarm, and is no longer protecting the connected equipment. When this happens, the protector should be replaced.