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Furnace troubleshoot for the homeowner
If the furnace does not start
Its cold in the morning, what do I do?
It may seem like a no brainer but check the thermostat. Is it turned up? Sometimes it is hard to tell. Check the following videos.
It may seem like a no brainer but check the thermostat. Is it turned up? Sometimes it is hard to tell. Check the following videos.
What to do nextIf the furnace still does not run, there may be no power to the furnace.
There are some simple steps to try: Check to see if your thermostat has a fan switch. If it is the "auto" position, switch it to the "on" position. The circulating fan should come on. If the fan comes on power is available to the furnace. If it does not come on, there may be no power to the furnace. |
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There are 2 videos below about what procedures to follow if the furnace does not start before calling the repair man. The first is a short version for those with some knowledge about repairs.
The video below covers a more complete procedures to follow before calling for repair service.
Filter problemsAll forced air furnaces should have a filter. It will usually be installed near the furnace. If the filter gets plugged there will be reduced air flow. Note the 2 filters on the left. The upper one is a clean pleated filter.
The lower one is also a pleated filter, but it is plugged. The bottom filter will not flow enough air to keep the furnace from shutting off on limit. If the filter is plugged, the unit will not heat well because the burner will not stay on. If it continues for an extended time, it can damage the furnace. |
What to do next
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If, after following these steps, you still have no heat, then it might be time to call for service.
If you want to try a few other things, continue on. If there is no heat and the fan is running blowing cold air and your furnace is less than 20 years old, it may be out on safety shut down. Newer furnaces have electronic controls that sense if conditions are not right for the furnace to run. If it is off on safety, some furnaces will lock out and turn on the circulating fan to let the customer know there is a problem. In this case there will be a small window (shown left) in one of the furnace doors behind which will be a flashing light. The light may be flashing a code which tells you what was the reason for the failure. The light may not tell you what part has failed but what safety caused it to shut off. If you shut off the power to the furnace, the electronics will reboot and the failure code will be reset. Sometimes after a reset, the furnace will run normally. More commonly, it will go out on the same failure code either right away or after a few minutes. For a list of furnace failure codes for different brands of furnaces, click here |
The videos above apply to most furnaces. The video below is about oil furnaces. It discusses what should be done to keep your oil furnace running year after year. It is not a repair video but rather one about procedures that will insure that it keeps running.
Relight the pilot
The video below shows how to light the pilot on a gas furnace
If you want to go farther into troubleshoot, and are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits. If you want to continue, you can try the troubleshoot page. Click here