furnace running while stat off I had the same problem once and found that the blower control board was defective, I have a carrier 20 years old, I was told to take the covers off and hold the lower safety switch in and there is a light that should be on, the board on mine was defective, I would check the fuse on the board, they are a car fuse, shutoff unit off … Most times the on/off switch for your furnace or boiler is labeled and red in color. I currently have 2 Nest (gen 1) units. Step 2 – Check Your Thermostat if Your Furnace Keeps Turning On and Off Repeatedly Touching the WHITE wire to the RED wire will turn your furnace on without the thermostat. Give it a few moments to see if the furnace cycles off. We turned off Heat and it kept running, we tripped breaker and now thermostat says bat low. First, make sure that your thermostat is switched on, and set to ‘heat’. You’ll want to look for things like disconnected or frayed wires, and you’ll want to make sure your thermostat is wired properly. My 2 yr old Goodman heat pump compressor comes on every 20 minutes for about 6 minutes AFTER it has reached the desired temperature. The batteries to power thermostats are standard batteries that you can buy at most stores. If I turn it up to 72 and then when it reaches 72 bump the setting down to 70 it will shut off. If the high limit switch goes bad, the furnace won’t shut down and the heat exchanger will crack. We turned off Heat and it kept running, we tripped breaker and now thermostat says bat low. Sometimes, the furnace is running constantly to keep up with the temperature, especially if it’s really cold outside. A clogged filter may cause the furnace's blower to run continuously because it can damage the furnace's limit switch. I have since swapped to my old thermostat so I will have to put the nest back up to check relative humidity (unless I can do this check without wiring … Have a furnace fan that runs continuously? A normal furnace is meant to run for a certain cycle to warm the home, and this is where … Put $0 down on central air and ductless AC systems. If the furnace was in the middle of a heating cycle, wait 3 to 4 minutes for the blower fan to stop running. On older furnaces, as a previous poster said, there is a temperature sensor that has ordinary metallic contacts that sometimes stick. If your thermostat is broke, you can purchase a new one at most home improvement stores for a fairly reasonable price. It is set at 72 degrees with an OAT of 50-60. Problem: Fan on your furnace runs all the time and will not shut off. So if your blower fan just won’t stop running, the first place to check is at the thermostat. The wiring could be old and need replacing, it might need new batteries, or it could be the location of your thermostat. Check that the thermostat FAN switch is set to AUTO not to ON. My AC or furnace keeps turning on and off repeatedly; My AC or furnace seems to be running more frequently than usual; I haven’t changed my temperature in my house, but my AC or furnace is still trying to turn on and off to fulfil a demand I haven’t made; Diagnosis. Unfortunately, in this instance, you will have no other choice but to replace your furnace if you want to correct the issue. To do this, feel the air coming out of the vent with your hand. For instance, if you set your thermostat to 100 degree when it’s below zero outside, your furnace will continue to run and struggle to hit that temperature. Settings such as low, medium or high cause the fan to run continuously regardless of the temperature that is reached in the space. If your thermostat is placed close to a heat source such as direct sunlight or a heat register, it will skew the temperature reading causing the thermostat to turn on and off irregularly. Type above and press Enter to search. Solution:. If you have an old thermostat that is not working properly, it could lead to your furnace constantly being on. There are several reasons this can happen. The only way to turn furnace off is to turn gas valve off and disconnect fan at electrical outlet Replaced thermostat with no change. Next, make sure that your temperature is properly … Once again, this is important to allow proper airflow to the furnace. Furnace fan still running? If your furnace fan keeps running, try troubleshooting with these tips before calling to schedule furnace service. Changing your filter will help keep the mechanical components of the furnace free of dust and dirt and may prolong the … Thermostat is too high. The Furnace Isn’t Derated Two settings that you’ll want to check are: 1) The fan setting. The furnace will run constantly to keep up on a cold night. It automatically shuts off the fire in the furnace if the temperature becomes too high until the furnace has the chance to … A thermostat positioned near a heat source or in direct sunlight can warm too quickly, signaling your furnace to shut off before the entire home is adequately warmed. If you have set your thermostat for 95 degrees in the middle of... 2. “Short-cycling” refers to your furnace coming on, running for just a few minutes, turning off, and running again repeatedly. If you forgot to charge the battery and your thermostat keeps running with the weak battery, it can affect your home HVAC … When this occurs, your furnace is failing to complete a full operating cycle as it is programmed to do in order to adequately heat your home. This is a common problem for homes with an undersized cooling system. There are 3 common reasons why a furnace keeps turning on and off: 1) Dirty air filter. Have someone repair or replace it. The Nest thermostat could never catch up and the AC was always running! According to our history in the Nest app, it fluctuates between Stage 1 and Stage 2. If the blower continues to run when the temperature of the blowing air is cool, then the sensor that shuts off the blower is defective. If your furnace keeps blowing hot air and won’t stop, the furnace burners aren’t turning off. Restart your Nest Thermostat by pressing the display for about 10 seconds. Another reason your furnace keeps shutting off could be the thermostat. This is why it’s best to get your furnace fixed as soon as possible. Michael Joseph has more than 20 years of hands-on experience as an avid home handyman and had 10 years in the construction industry, specifically in the field of HVAC. You are not alone. The limit switch is designed to detect the temperature inside of the furnace. 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