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Furnace Repair: First Things To Check When You Have No Heat

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If your furnace is running like mad but your house is colder than you would like it to be, you may need some furnace repairs. Before you call a technician, there are a few things you can check on your own. Checking these things will help you answer any questions the HVAC contractor asks over the phone and rule out what he/she thinks is the problem.


Regardless of what type of furnace you have, there are still some electrical components involved. If you have a boiler, there is some electricity needed to boil the water and create steam. An electrical furnace is electrical all the way, and a gas furnace still needs electricity to operate the fans that create forced air and push it into the ventilation system.

For each of these, you will want to check:

  • Power box/fuse box connections; make sure the fuse switch is on
  • Any on/off switches located directly on the furnace or boiler, which may be switched off and causing your lack of heat
  • Exposed wiring for disconnections or fraying (do not touch--look only)

If there is anything suspicious with the electrical, take note and inform the HVAC person of what you see. If not, move on to the next possibility.

Heat Source

If you have a boiler, you will need to check the ignition, heating coils and any other parts that you can see. If you cannot see or open parts of your boiler for safety reasons (and please do not open them!), use your hand to feel the areas and parts of the boiler that should be really hot. If they are not, your boiler has a problem internally with the components that heat and boil water and/or produce steam.

If you have an oil furnace, check your fuel tank to make sure it is not low or empty. You would be surprised how quickly you can use up heating oil and not realize that it is gone. Also, check the pilot light, the ignition switch and your fuel lines. Clogs, even little ones, can quickly choke up the fuel and make it impossible for your oil furnace to burn enough fuel to produce enough heat.

If you have a gas furnace, again check the pilot light. The pilot light should be blue for propane, and a similar color for natural gas. If you do not have a light, then there is nothing burning the fuel coming out of the line. This is dangerous and you should try to shut off the gas valve and leave the house immediately to call the furnace repair contractor to deal with it.