Furnace not kicking on?

Why is my furnace not kicking on?

The furnace kicking on is then worst feeling when your house is freezing cold. A cold night in St. Charles MO you come home and the house has frozen over. This is no fun we all know that. Therefore, you just walked over to the thermostat, and it does not kick on.  Therefore, you start to panic and freak out. There is many reasons that can cause this issue. It can be from big too small.
Let us hope you just woke up from a dream and that did not happen because you have a maintenance program. Let us diagnose…

Firs off some easy points of problems why your furnace is not working

  • Power
  • Wear and tear
  • Malfunctioning thermostat
  • Furnace wouldn’t heat
  • Furnace is to noisy
  • Pilot light or electric ignition
  • Blower runs constantly
  • Furnace kicks on and off
  • Not Enough Gas
  • Thermostat
  • Blower Motor


Power– So you have a gas or electric. It does not matter you need power for both to get the furnace to kick on. Check your circuit box downstairs. Also, check around the unit and the box and see if any critters have been munching on your wires.

Not Enough Gas– So this is still one you can perform on your own. Take the time to check the valve is completely on. Many times a furnace does not kick on because the valve is half turned. Remember when the furnace not kicking on you should have the valve completely on or off.

Blower Motor- Most blower motors have what we call an inspection window on the furnace. Obviously, that does little if you have no idea what you are looking for.  The flashing green light lets you know everything is okay. If you are seeing the red light then you are having issues. When your contractor comes out, they will inspect the control board, motor and transformer.

Thermostat– I would recommend before you finally decide to call the O’fallon, HVAC Contractor, you should look over your thermostat. Many of the new digital thermostats have fail-safes and different modes that could cause it to kick off.

Gas Supply– Kids play and turn things all the time. You will want to check your gas valve and make sure nothing is off. Some homeowners turn down the valve during the summer months. So check your valve and make sure it is open.

Furnace Repair O'Fallon, MO


Furnace Power Issues

Thermostat Issue- Check the thermostat I know I know. This sounds silly. Make sure you have it set to heat please. In addition, if it is 40 degrees outside and you have it set to 38 it will not kick on. It should be set to higher than what it is showing. Also, if the thermostat has been switched to fan please change it to heating. Very commonly forgotten step.

Pilot Light- Get down and check for the blue pilot light. This is a very common thing. Not as much with new units but it can still happen. When you get down there look around for a flame check everywhere. Normally it is easy to find but still look very hard.  If you do not see the pilot light use a match and light it, back up. So call us first and we will walk you through where to stick the match.

Condensation- A condensation pan on the furnace collects excess water and if this gets full, it will cause the furnace not kicking on. Normally draining of the pan is not an option although it could work temporarily. Just remember this did not fix the issue that caused the pan until fill with water. We have seen blockage that prevented water from draining. In addition, we have seen a bad condensation removal pump.

Air Filter- 1 of my favorite because it is the cheapest for you is the dirty old air filter. You have to be aware of and maintain your air filter. See our section on air filters here. The changing of an air filter can take less than a minute if you are into NASCAR even faster than that. Remember keeping that air filter clean can save hundreds of dollars over the life of the furnace.

Loose Wires-– Vibration can cause wires to come lose all the time. At some point, all of the vibration will rattle a wire loose. Fixing the wire is very easy. The tricky part will be figuring out where the wire connected. You will want to make sure it is plugged into the right spot.  When you have your inspection done each year. They will check all of the connections and make sure nothing is loose.

Fuses– One of the easiest ways to know if you are having issues is check your fuses. If you have a blown or lose fuse you will not have power at all. You have to remember these machines are so easy but so hard to work on. Buy a new fuse and replace it with the same amp.

Dirty Fuse– Furnace maintenance is so important. Dust and debris builds up over the years. Check your fuses.

Starting Capacitor– Sometimes a starting capacitor is not giving enough power to the system to kick it on. Replacing your capacitor is an easy and cheap fix.

Gas Valve– You could easily have a failing gas valve in your lines. When debris gets in the valve, it can make it hard for it to open or close. When this happens, it will heat up then the system will short and blow a fuse.

Electric Furnace Repair


Your electric furnace is going to be much different from your gas furnace. The control board is going to be your main source of power. Generally, everything is controlled from there. Unless you know what you are doing, I would not recommend messing with it. Call your local contractor to have it fixed.


If you have any thoughts or ideas on why your furnace wouldn’t kick on let us know below.

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