If you suspect your furnace keeps shutting off because of this, or another internal issue, book an appointment with us. The board, like most computer systems, may just need a restart. Call a pro if you’re unsure about performing the tests yourself. Hi.. If your furnace overheats, the high limit switch will kick on. Furnace blower fan keeps turning off when using A/C. To help keep your furnace from constantly turning on and off, make sure that you change the air filter at the start of each new season and check it monthly. Don’t freak out just yet though, because by reading this article I’d give you no less than a 50/50 shot that your furnace issue is something you can handle yourself. We use cookies to give you the best possible experience on our website. We replaced the air filter and thermostat, same issue. What could be the problem? As a temporary solution, while I waited for my replacement, I hooked my W1 (furnace) to Y1 (cooling) and turned the temp down. DAN THE AC MAN. Its not like it turns on or off for minutes at a time, its almost constantly switching on and off, it will switch on and then before it has time to even get to the full speed setting it would turn off again. Here's Why Your Furnace Keeps Turning Off. If this doesn’t work, turn off the power and gas supply to the furnace. [ 20 Answers ] Here's my issue. Flame Sensor. Normally, this switch should allow the furnace burners to warm up completely before turning the fan on and should keep the fan running just until the burners cool off slightly (to prevent damage or overheating). Your furnace’s heat exchanger needs that air blowing over it or it overheats, causing the furnace … Some other possibilities (if applicable) would be: a blocked/clogged flue, a dirty flame sensor, or a faulty furnace blower motor (very uncommon). You should also test your thermostat to ensure it’s working correctly. It runs good heat. Hello, This past winter I installed a Nest v3, and it worked great all winter with our forced hot air system. But lately it's been turning on and off. Update: the blower will turn on then go off three or four times before staying on. However, I can turn on the blower by manually pressing a 'Manual On' button inside the furnace. This sends the incorrect message to your furnace so your furnace shuts off. The fan will turn on as usual then about a minute later it will turn on for approximately 30 seconds, turn off for one or two minutes, then back on for 30 seconds. Your flame sensor is what properly gauges how much gas is going to your furnace. When your home becomes cold a short time later, your furnace starts up again. It will do this 3 or 4 times until it finally stops. gas forced hot air furnace - Answered by a verified Home Improvement Expert. Furnaces are calibrated to turn on and off based strictly on changes in indoor air temperature. HELP PLEASE :) If your furnace keeps turning on and off and you would like our furnace repair team to come out and troubleshoot and repair … Furnace Blower Fan Wont Turn Off - Hello Richard, I have a problem with my furnace where the indoor blower will turn off.My furnace seems to be heating okay it is just the blower will not shut off. Your Furnace … ... Blower does not come on. After the furnace stops running the fan/blower runs as usual. A furnace could potentially not turn off for a few different reasons. The AC unit outside would shut off when the set temp was reached, but the fan inside continued to blow. 1 decade ago. Answer: Being able to interface the Aprilaire humidifiers to turn off and on with the furnace blower or gas would depend on whether you have “HUM” (humidifier) hookups on your furnace’s control board. This is a repair that needs to be handled by professionals. Which is getting very annoying in this cold weather. This is most common cause of short cycling. Without touching it, inspect the heating element for cracks or damage and the wiring for any frays or possible malfunction. This is a safety feature that will turn your furnace off. Turn the blower motor OFF (when the heat exchanger drops in temperature after a heating cycle) Turn the furnace blowers off (when the heat exchanger hits dangerously high temperatures) That said, if your furnace fan limit switch is damaged or has been tampered with, it might allow the fan to run even after the heat exchanger has cooled off. I have a fairly new furnace. This is not normal behavior and the problem is unlikely to clear up on its own. I tested by jacking the temp from 65 to 75, and it ran straight for 20 mins, then again cut short of the temp. What could be wrong???? Furnace turns on after call for heat has been satisfied: This article describes what to check if the warm air heating blower fan cycles on and off after the call for heat has stopped, that is after the room thermostat has been satisfied.. Answer Save. Source. Dirty air filters are a common cause of furnace cycling problems. Thermostats near heat sources or in direct sunlight can warm too quickly, signaling your furnace to shut off. It is an older furnace, and I have checked the thermostat settings. Once the furnace has sufficiently warmed the home, it is typical for the blower to slow down. That’s no good. Let’s take a look at the most common causes for a furnace that won’t shut off: For other common problems, see: Furnace Keeps Turning On and Off … Allowing your furnace to continue short cycling can cause permanent damage to the boiler. Lv 5. These 90% furnaces may start-up and run fine at the beginning of the season as the blockage absorbs the condensation and may even drain with no negative results. Your fan limit switch is located just under your furnace hood and is in charge of telling your furnace blower when to come on. Diagnose furnace blower problems: this article describes what to check if the warm air heating blower fan cycles on and off after the call for heat has stopped, that is after the room thermostat has been satisfied. So it shuts off the gas valve. My furnace keeps turning on every 8 minutes, runs for 3 minutes and shuts off for 8 minutes again. Blower on furnace keeps turning off and on when the furnace isn't calling for heat. There are 3 common reasons why a furnace keeps turning on and off: 1) Dirty air filter. Question: My humidifier runs all the time, even when the furnace is off. But sometimes, furnaces will begin turning on and off too rapidly to be responding to temperature variations. The Guide to Troubleshooting a Short-Cycling Furnace. Replacing the capacitor and cleaning the filter should be enough to get your furnace up and running again without the annoying humming sound. Just contact us and we can get your furnace fan running normally in no time. Gas and Oil Home Heating Furnaces - Furnace keeps turning on and off - So my furnace control board shorted out a few weeks ago so I replaced it. Relevance. Solution: Replace the air filter. - AC … Why is My Furnace Leaking Water? AC , Furnace, and Blower not turning on w/ thermostat set to Auto or On. If the line becomes clogged, it can trigger a safety feature that keeps the burners from lighting. … Drain line appears to be clog free as water is dripping from it. I've been noticing that since I've had my heat on these past few cold days, my furnace kicks off before it has even reached the set temp on the thermostat, and a min or two later, turns back on, and keeps doing it. As a result, the blower continues to blow cool air to cool down the furnace. Why is My Furnace Turning On and Off: Common Problems and Solutions Problem: Dirty Air Filter. 4. The term we use to describe a furnace that keeps turning on and off is “Short Cycling.” This problem originates from inside the heating system. Now that summer is here, I tried using our A/C system for the first time with the new Nest. See if the furnace works. My blower/heating system has developed a little glitch where it turns itself on and off while blowing air at any speed setting. The fan limit switch is responsible for turning the blower on and off at the appropriate times. Bit of background: The furnace blower originally did not not turn off at all (or if it did, very rarely did so), even when set temps were reached or when the system was off (fan setting is set to auto, not on). If your furnace is coming on and isn't turning off, you need to investigate the issue, as it could end up costing you excess money on your utility bill at the end of the month. Bypass the Nest by turning off the power to the furnace, attach Rc and W1 together, restore power. It is the time of year here in Mich where I have the AC … Step 1 Replace your "furnace limit switch." 2 Answers. My AC tech, via text, had me remove the float in the air handler to see if it would come on and stay on, it did not. Step 1: Locate your fan limit switch. A dirty air filter restricts air from getting into your furnace. Your fan limit switch is located inside the furnace panel cover, usually near the upper right corner. Have you ever thought "Why does my furnace keep shutting off? Along this same vein, another sign that you might need a new capacitor comes when your blower slows down too much. Problem: Furnace Short Cycling. Why Is My Furnace Clicking: 3 Common Furnace Concerns ... or limit switch, to turn off the burners. Some basic furnace troubleshooting will help you determine if the issue is something you can fix or something that requires expert attention. I cannot turn on either my AC, Furnace, or Blower from the thermostat. If it does, the Nest is the problem. The blower won't come on for 30-45 minutes after the AC has been turned off, but after that it seems to turn back on fine. This is a very common problem that if not diagnosed and corrected immediately could result in higher utility bills and major furnace repairs. Testing your thermostat can involve handling live wires. The Blower motor on my AC unit turns off at random times while the outside unit continues to run which is causing the coil to freeze up. Favorite Answer. 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