Furnace Repair in McHenry, IL

HVAC man working on a furnace

When your heating system won’t kick on, doing your own furnace repair in McHenry, IL, can feel daunting.

There are a few time-saving, inexpensive solutions you can take on yourself to avoid a HVAC service call.

If your heater won’t start, won’t stay on or won’t light, try the troubleshooting guide below before getting in touch with an HVAC pro.

If you discover you need assistance from a heating and cooling pro and live in McHenry, Jett's Heating & Air Inc. will be able to provide assistance to you. We are able to repair most makes of heaters.

CALL NOW 815-410-1128

If you’re ready for a new heating system, we also offer furnace installation.

While you’re chatting with one of our team members, think about a regular furnace maintenance plan from Jett's Heating & Air Inc. that may help you avoid breakdowns down the road. A team member can let you know how regularly your furnace should be checked by one of our certified professionals.

Follow our easy checklist as demonstrated to get started on troubleshooting your furnace. A great deal of these procedures don’t have a need for mechanical abilities to complete your furnace repair.

Furnace Repair Checklist

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1. Examine the Thermostat

To start, make certain that your thermostat is telling your furnace to start.

Digital Thermostat

  • Swap out the batteries if the screen is empty. If the digital monitor is mixed up, the thermostat may need to be swapped out.
  • Make certain that the button is switched to “heat” rather than “off” or “cool.”
  • Make certain the program is set to the appropriate day and time and is programmed to “run.” If you’re having problems overriding the setting, set the temperature by utilizing the up/down arrows and using the “hold” button. This will cause the furnace to ignite if thermostat is causing a problem.
  • Turn the temperature setting to 5 degrees warmer than what the room temperature currently is.

If your heat hasn’t turned on within a few minutes, make certain that it has juice by switching the fan switch from “auto” to “on.” If the fan doesn’t begin to run, your furnace might not have power.

Smart Thermostat

If you use a smart thermostat—such as one made by Nest, Ecobee, Lux, Honeywell or Bosch—troubleshooting will be determined by the model you have. Check the manufacturer’s website for assistance. If you’re still unable to get your Wi-Fi thermostat to operate, reach us at 815-410-1128 for heating and cooling service.

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2. Examine Breakers and Switches

Next, verify your breaker and furnace switch are on.

  • Find your main electrical panel. If you have no idea where it is, look for a metallic metal box in your basement, garage or closet.
  • Ensure your hands and feet aren’t wet prior to using the panel or breakers.
  • Look for the breaker marked “furnace” or “heat,” and ensure it’s switched “on.” If you find that the breaker tripped, it will be in the middle or “off” position.
  • With one hand, steadily flip the breaker to the “on” position. If the breaker instantly trips and pops back to “off,” don't try to reset it and contact a professional from Jett's Heating & Air Inc. at 815-410-1128 right away.

No matter your furnace’s age or brand, it has no less than one standard wall switch set on or by it.

  • Make sure the control is moved up in the “on” position. If it was turned off, it could take your furnace up to five minutes to start. (If you’re unaware of where to locate your furnace, take a look at your basement, garage or utility closet. It might also be in a crawl space or attic.)
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3. Put in a New Air Filter

When we think about heating problems, a dirty, clogged air filter is often the top culprit.

If your filter is too dirty:

  • Your heating system won’t keep heating your home, or it could overheat from reduced airflow.
  • Your gas expenses might increase because your heat is turning on too often.
  • Your heater could fail sooner than it should due to the fact a filthy filter forces it to work overtime.
  • Your heater might be disconnected from power if an overly clogged filter is the cause of a tripped breaker.

While it depends on what model of heating system you use, your air filter will be in the interior of the blower compartment of your heating system, an attached filter case or wall-mounted return air grille.

To put in a new filter:

  • Switch off your heater.
  • Remove the filter and tilt it toward the light. If you can’t see light through it, replace it.
  • Insert the new filter with the arrow pointing toward the furnace to avoid damage.

Flat filters need to be replaced every month, while pleated filters should last about three months. If you have children or pets, you could have to put in a new filter more often.

To make the process smoother in the future, use a permanent pen on your heating system outside or ductwork to show the airflow direction and filter size.

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4. Examine the Condensate Pan

Also known as drain pans, condensate pans catch moisture your heater draws from the air.

If moisture is seeping from your furnace or its pan has standing water in it, use these recommendations.

  • If your pan has a drain (look for a PVC pipe), make sure that it isn’t full. If it requires draining, use a special pan-cleaning tablet you can purchase at home improvement or hardware stores.
  • If your pan has a pump, inspect the float switch. If the lever is stuck “up” with liquid in the pan, contact us at 815-410-1128, because you will probably have to install a new pump.
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5. Check for Heater Error Codes

If faults continue, take a look inside your heating system’s plastic window to verify the blower motor’s status. Subject to the model, the light might also be mounted on the exterior of your furnace.

If you note anything else besides an uninterrupted, colored light or twinkling green light, reach us at 815-410-1128 for HVAC service. Your furnace might be communicating an error code that is calling for pro help.

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6. Clean the Flame Sensor

If your heating system attempts to start but shuts off without putting out warmth, a grimy flame sensor could be responsible. When this happens, your heater will make an attempt to turn on three times before a safety device turns it off for approximately an hour.

If you feel okay with taking the panels off your furnace, gently scrubbing your flame sensor is something you are able to do personally. Or, one of our heating service professionals is able to complete it for you.

If you are fine with cleaning the sensor personally, you should have:

  • A 1/4” hex screwdriver or wrench
  • Piece of light grit sandpaper, steel wool or emery cloth
  • A dry, clean paper towel


  • Shut off the furnace’s power by using its wall switch or breaker. If your gas valve isn’t electric, you must turn off the gas in addition.
  • Remove the heating system’s front panel and trace the wire to the flame sensor.
  • Unscrew the rod and use your sandpaper, steel wool or emery cloth to lightly rub the metal rod.
  • Clear the rod with a paper towel.
  • Put the sensor back in.
  • Put the furnace doors back on.
  • Switch the furnace’s power back on. It might go through a set of examinations before resuming regular running. If your furnace doesn’t ignite, the sensor could have to be replaced or something else might be wrong. If this takes place, contact us at 815-410-1128 for heating and cooling repair support.
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7. Reignite the Pilot Light

If you have an outdated heater, the pilot light could be extinguished. To reignite it, locate the steps on a label on your heating system, or use these steps.

  • Look for the toggle on the bottom of your furnace marked “pilot,” “on” and “off.”
  • Turn the switch to the “off” position.
  • Take a break for at least five minutes to avoid creating a fire.
  • Turn the knob to “pilot.”
  • Hold down the “reset” button as you bring the flame of a long lighter to the pilot light opening.
  • Depress the “reset” lever once the pilot light is lit.
  • If you have followed the guide twice and the pilot light still won’t ignite or remain lit, call us at 815-410-1128 for furnace service.

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Check Your Fuel Source

Try turning on a second gas appliance. If it doesn’t work, your natural gas source may be turned off, or you might have run out of propane.

We Can Provide Furnace Servicing

Used our troubleshooting checklist but your heater still doesn’t work?

Contact us now at 815-410-1128 or contact us online. We’ll visit your house and diagnose the problem.