Lennox Furnace Troubleshooting

Lennox is a reputable HVAC company manufacturing highly rated gas furnaces around the world. But the products can still have mechanical problems at times.  This troubleshooting guide ought to help you in determining and resolving the problems before you call a furnace repairman.

The Lennox Furnace Doesn’t Start

If the furnace is unable to provide enough heat, check the thermostat first. It should be in the heating mode and the temperature should be set to a point higher than the room temperature. Make sure the circuit breaker in the electrical panel has not been tripped and also the on/off switch on the furnace is in the “on” position. If still the furnace is unable to perform properly, it indicates that there is something wrong with the thermostat.

The Lennox Furnace Doesn’t Fire

In case the inducer motor runs but the furnace doesn’t fire, it is possible that the vent is partially blocked by dirt, snow or debris. Also make sure the gas valve is in the ‘on” position and the tank is filled with the fuel. If the hot surface igniter never glows hot while the furnace tries to start, you must readily replace this glow plug. If the pilot light doesn’t stay still, your thermocouple may be bad. You should call a certified technician to get it replaced.

The Lennox Furnace Turns Off Immediately

If your furnace fires but shuts down immediately, there are a number of reasons that may occur. Maybe the unit is overheating because of a dirty or clogged filter. Therefore, it is better to clean the filter or get it replaced. Also make sure the condensate reservoir is not full, and if it is, clear the drain. If you are unable to clear it, the pump is not working properly. Another possible reason for the immediate shutting down of the furnace is the heat sensor. Clean the heat sensor thoroughly or get it replaced if necessary.

The Lennox Furnace Blower Doesn’t Turn Off

If the furnace blower keeps on running, first of all check the thermostat settings and make sure it has not been switched to “fan continuous” selection. There will be a dial with a series of numbers around its circumference next to the “fan-limit control” red button. Set the dial to the required number of hours you want the fan to run, and if fails to do so, it indicates a faulty fan-limit control panel which should be replaced by a HVAC service repairman.

The Lennox Furnace Control Board

The furnace control board is often referred to as mother board as it controls all the major operations of a gas furnace. If you are unable to identify any obvious problem accountable for the improper working of the furnace, then the control board is to blame. A faulty board may cause a number of problems: it may prevent the furnace from starting; the furnace won’t fire; or it may also prevent the blower from starting. If you see an electrical surge knocking out of the control board, it is an obvious sign of a burned board which should be replaced as early as possible.

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