AC air handler buzzing sounds. Do you hear a buzzing sound when you turn on the thermostat? The only thing that comes on in the house when you turn on the thermostat is the fan relay and fan in the air handler or furnace. Try switching the thermostat HEAT/COOL switch to OFF. Then switch the fan switch from AUTO to ON. The fan (only) should come on. If the air handler makes a buzzing sound, it probably has a bad fan relay or, more likely, blower fan.
If your AC doesn’t turn off when room temperature reaches the temperature set on the thermostat, the problem is generally occurring either at the thermostat or in the electrical system that runs the outside condensing unit. You can use the AC’s circuit breaker to shut off the unit, but that should not be a permanent solution—circuit breakers are not designed to be used like light switches.
For starters, once a year, vacuum out the area around the furnace’s blower. If possible, also slide out the fan unit, clean each fan blade with a toothbrush, and then vacuum with a brush attachment on a vacuum cleaner. While you’re at it, look for oil ports on the motor, normally located near the motor shaft. If the motor has these, apply two to three drops of non-detergent motor oil into each port (you may have to remove a cover plate to do this). Though most contemporary motors don’t require lubrication, do lubricate motors with oil ports once a year. For more about maintenance, see Maintenance Checklist for Central Heating Systems.
For starters, once a year, vacuum out the area around the furnace’s blower. If possible, also slide out the fan unit, clean each fan blade with a toothbrush, and then vacuum with a brush attachment on a vacuum cleaner. While you’re at it, look for oil ports on the motor, normally located near the motor shaft. If the motor has these, apply two to three drops of non-detergent motor oil into each port (you may have to remove a cover plate to do this). Though most contemporary motors don’t require lubrication, do lubricate motors with oil ports once a year. For more about maintenance, see Maintenance Checklist for Central Heating Systems.
Finally, don't underestimate the thermostat as a potential reason why your furnace is not working. Everything on the heating unit itself may function perfectly, but your home still will not heat right if the console you use to set the temperature doesn't communicate your input. A faulty thermostat can either be due to the wall unit itself, or the wiring that connects it to your furnace. Average thermostat repair costs are between $108 and $282, including labor. Replacement costs, of course, depend on the thermostat you choose. Visit our thermostat repair cost guide to learn more about this type of issue.

Cut down on energy costs and prevent damage to your furnace by addressing a gas furnace that's overactive or short cycling. Besides the need for consistently comfortable temperatures, this issue could cause long-term safety issues to your home, making it very important to address. From a faulty thermostat to a dirty filter, there are several possible causes to investigate.

×