Forced air heating or cooling air handler troubleshooting: blower fan won't shut off: This article describes what to check if the furnace or forced air blower fan does not stop when you expect it to do soThese same diagnostics also aid in air conditioning blower assembly diagnosis when an A/C blower continues running. We explain what switches or controls may be set improperly or what else, such as a shorted wire, can cause continuous HVAC fan operation. First, confirm that the room thermostat is not calling for heating or cooling. In the heating season, just set the thermostat(s) to the lowest setting and confirm that room temperature is above that point. In the cooling season do the opposite - set the thermostat to its highest setting and confirm that room temperature is below that point. You have told the thermostat to turn off the HVAC equipment. If the equipment was running give it three to four minutes to shut down. Next: If the blower just keeps running no matter what, there are two places to check switch settings before calling your heating or air conditioning service company in response to a furnace fan or air conditioning fan that just keeps running without stopping:

1. At the room thermostat: the FAN-AUTO-OFF or FAN ON/OFF switch on the room thermostat should be checked. The fan control should be set to AUTO. You can try turning the switch to OFF too. Details of checking the thermostat's FAN-AUTO-OFF or FAN-ON switch position when the furnace (or air conditioning) fan won't stop running are at FAN WONT STOP - THERMOSTAT SWITCH Other snafus such as a shorted thermostat wire can also cause the A/C or warm air furnace fan to run continuously. Those problems are explained at THERMOSTAT WON'T TURN OFF. 2. At the furnace or air conditioner air handler or blower unit: the FAN LIMIT SWITCH may include a switch that manually keeps the fan running. We discuss this switch here. Take a look at the fan limit control switch. Before pulling the cover off of the switch, just see if the switch includes a control such as the white push-pull switch like the white device shown at the lower left in our photo. Depending on the position of this switch (pushed-in or pulled out) the fan may be on manual override - causing the fan motor to run continuously.

Check the printing on the switch face to see if you should push the switch in or pull it out to leave the blower on "Auto". ("Man" or "Manual" would be forcing the fan to run.) Usually: "Push-in" position on this (Honeywell) fan limit switch is for continuous fan operation and "Pull out" position is for automatic fan operation.Primitive Curtains Cheap There are some reasons (explainedCheap Patio Furniture Baltimore at BLOWER FAN CONTINUOUS OPERATION) to leave the blower fan on continuously for long periods, such as to use an air filtering system to improve indoor air quality. Furnace Blower Motor SupplyAnd in some buildings we may run the blower continuously for more even or better conditioned (heated or cooled) air distribution.

On the off chance that someone has inadvertently mis-connected or shorted fan control wires at the fan limit switch, also check out FAN LIMIT SWITCH INSTALLATION. On the chance that there is a shorted thermostat wire, a problem that can also cause the A/C or warm air furnace fan to run continuously see THERMOSTAT WON'T TURN OFF. Details about the manual FAN ON or FAN AUTO ON switch right at the furnace or air handler at the manual at BLOWER FAN CONTINUOUS OPERATION. This article series answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. My fan keeps running with no heat on furnace. What can I do? If the furnace does not even try to run, that is if it never even starts, then follow these steps:

If the furnace tries to start but cannot keep running then there is a different problem such as no fuel or an unsafe condition. See DIAGNOSE & FIX HEATING PROBLEMS-FURNACE - home A complete list of oil and gas fired furnace controls is at FURNACE CONTROLS & SWITCHES Continue reading at FAN LIMIT SWITCH or select a topic from the More Reading links or topic ARTICLE INDEX shown below.Staying on top of your central air conditioner can save you big money on repair bills. Any number of small items can render your air conditioner inoperable. Before calling a repair service, troubleshoot some of the common air conditioning issues that cause a unit to fail. You can fix many of these items on your own, without the help of an HVAC professional. Check the Thermostat Check your thermostat to begin your central air conditioning troubleshooting. Make sure the thermostat switch is in the "on" position, and it's set to "cool." If the thermostat is a digital model, replace the batteries if applicable.

Verify the temperature setting on the thermostat is lower than your room’s current temperature. Many times, thermostat settings cause the trouble. If the inside unit fails to come on once you've checked the thermostat setting, check the fan switch. The fan switch should be set to "auto" and not "off." If the switch is set to "auto," move the switch to the "on" position. If the fan does not come on, check the circuit breakers. Replace the Air Filters Check the air filter inside your unit if it still doesn’t produce cool air. Pull out the filter and inspect both sides. If the filter appears dirty and clogged, you must replace it. You should clean or replace your air filter once a month to keep the unit working properly. A clogged air filter will cause the unit to work harder, overheat and not cool as efficiently. Check the Circuit Breakers Your air conditioning unit has two breakers; one operates the outside unit while the other operates the inside. If the breakers appear tripped, turn the breakers off and then back on to reset them.

If the unit comes on briefly once you reset the breakers, but they trip once again, call an air conditioning service provider to check the electrical wiring. Check the Condensate Drain If resetting the breakers turns the unit back on, but the unit still won’t cool, check the condensate drain line. A float-switch safety device sits inside the drain. Should the line clog, the float-switch turns off the unit. This stops the creation of condensate that could overflow, damaging the unit and your home. Attach a wet/dry vacuum to the condensate drain line outside your home to ensure it is free from clogs. Check the condensate drain line inside your home while running the vacuum. You should hear air rushing through the line. This means the vacuum has removed all excess water and gunk built up inside the drain. Once you've completed the inside central air conditioning troubleshooting, check the outside unit. Check the Outside Safety Disconnect If the inside unit is operating, but the outside unit is not, check the disconnect switch on the exterior wall.

This separate safety shut-off switch allows an air conditioning service provider to interrupt the power to the unit when making repairs. If the disconnect switch is in the "off" position, turn it on to see if the outside unit starts. If it doesn't start, check the switch fuses. Test the fuses with a continuity tester if you feel comfortable working with electricity; if not, you may need to call a professional. If the fuses are good, and the disconnect switch is in the "on" position, it may be the dual capacitor or the fan motor. Check the Outside Unit The outside unit requires both the fan motor and a dual capacitor to operate the condenser. If the fan isn't turning, but you can hear the condenser, have your fan motor replaced as this puts too much strain on the condenser. If the fan motor isn't running and you cannot hear the condenser, have a professional check the dual capacitor, as it may need replacing. References InspectAPedia: Air Conditioning Diagnosis, & Repair GuideCarrier: Troubleshooting GuideYork: Air Conditioner Troubleshooting GuideDon Vandervort’s Home Tips: Air Conditioners – Central Photo Credits Jupiterimages/liquidlibrary/Getty Images Suggest a Correction