- Shortage of hot water
The most common gas furnace faults associated with cool air are:
- The furnace air filter may be clogged
- The gas burners in the furnace may need to be adjusted or may be dirty.
Troubleshooting:
If you have a permanent type furnace air filter that can be washed, it should be washed. Non-permanent air filters should be replaced.
If your burners need adjustment it is best to call in a professional.
- The gas furnace cycles on and off to often
The most common gas furnace faults associated a furnace that cycles on and off to often are:
- Clogged furnace filter
- Defective blower motor
- The heat anticipator in the thermostat is out of adjustment
Troubleshooting:
If you have a permanent type furnace air filter that can be washed, it should be washed. Non-permanent air filters should be replaced.
The blower motor should be lubricated. There are usually two ports one at either end of the motor. Use a couple of drops of light weight electric motor oil in each port.
Note; take care not to get any oil on the fan belt or the fan belt pulleys as this will cause the fan belt to slip.
Fan belts will expand over time and there can be slippage in the fan belt pulleys. Adjust the fan belt tension so there is approximately one inch of flex at the center of the fan belt’s span.
Note: If a fan belt is frayed it should be replaced.
Adjust the heat anticipator in the thermostat.
- Blower is always running
The most common gas furnace faults associated a furnace blower that is always running are:
Figure 4 - Thermostat fan on auto switch
- The thermostat has a fan control and it is set to on rather than auto, as shown in Figure 4
- The furnace has a defective fan limit control switch.
Troubleshooting:
Switch the fan control on the thermostat from on to auto.
The furnace fan limit switch control needs to be reset or if that does not stop the blower from operating all the time then the fan limit control switch should be replaced.
Note: A furnace fan will operate for a period of time after the burners have shut off in order to cool the burner assembly and not allow excessive heat to build-up in the furnace.