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Furnace lost flame sense

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. It only takes a minute to sign up. Over a year ago after a month in our new house, we came back one evening to a cold home and after some googling, I found out that the flame sensor was dirty and the furnace was starting the flame and then quickly puffing it out.

I cleaned the flame sensor and everything was normal again for two weeks. The flame sensor would fail every two weeks and every time I would clean it up and put it back in and everything would be okay. This made me very frustrated, so I talked to a number of HVAC stores, and none had any idea what was precipitating the situation. Finally, a lady at one HVAC store told me it was the lint from the laundry drier that happens to be too close to the furnace and that there is nothing that can be done about it if the laundry machines share a room with the furnace in the basement which is in fact the case in my house.

Nevertheless, I bought a brand new flame sensor and replaced my sensor. The new sensor held up fine for a month and then failed and needed cleaning and started failing every two weeks after the first cleaning.

I am now very frustrated and concerned about what would happen if I was to go on a prolonged vacation in winter. This would specially be a problem since my spouse is not handy and she would simply have to freeze waiting for an HVAC technician if this ever happened while I am away.

I should mention that my furnace is high-E newly installed Goodman furnace running on natural gas in mid-western Canada 3 years. I strongly suspect that something is not adjusted correctly, and you have excess soot production lint seems like a red herring, frankly which is making the sensor "dirty.

This is almost certainly a problem with combustion, not the sensor. The sensor fouling is a symptom, not a cause. I don't really regard this a great area for DIY - without the right tools, which cost more than most homeowners including me will spend, and the right training to go with them, screwing up combustion appliances though self-service is more common than tuning them perfectly.

There's also "not creating a giant loophole for your insurance company if the house burns down" as a minor factor in that thinking. Having burners professionally serviced on a yearly basis is a minor expense, comparatively. If as is commonly the case with high-efficency burners the furnace has both an air intake from and an exhaust to outside, the dryer lint really can't be the problem.

Some sort of blockage of that intake couldhowever, potentially cause the problem you are having insufficient air supply causing a rich, sooty flame; soot fouling the sensor. The flame sensor is only as good as the circuit board it plugs in to, that "thinks" about what it's getting. Have you considered that the control board might be goofy? They do go bad, too. After cleaning the flame sensor, checking ground wire, checking exhaust for cracks or blockage and the board connection which did not fix it.

We found that the hanger on the exhaust pipe was hung poorly and causing exhaust pipe to droop down which made it hold condensation that ran back into unit which shut the furnace down. Fixed hanger to make exhaust pipe level and it seems to be working now. Could also be that your thermostat is no longer sensing the correct temperature and causing your furnace to remain on longer in the heating cycle than usual. This causes the burner to heat up the flame sensor and cause it to become dirty sooner than just a yearly maintenance.

Also, is it a 2-stage induced draft motor? When your furnace comes on initially, does the small motor induced draft motor come on loud and really fast?

If so, then its immediately starting in 2nd stage which should not happen. This opens up the gas pressure on your gas valve and allowing high burner operation and giving your flame rod more flame and causing it to also become dirty sooner.

Phosphates from your washing machine detergent are plating on your flame sensor. Get your combustion air from outside and problem will be solved. By law you should have furnace in big enough area to consume proper air flow. If your furnace is btu you need cu ft of space. Room size X ceiling height is actual cu ft. If you have a hot water heater and dryer in same room you will have to add that btu rating to the calculation.I have a gas furnace model Lennox g34ufb This is the sequence of operation when it does NOT ignite:.

Thermostat calls for heat operation, and the blower fan starts.

Flame Sensor for Furnace

I see a glow in the burner area, then I hear a click from the gas valve this is where it usually ignites but no ignition. This process repeats 3 more times then the LED's flash slowly alternating, indicating "a Watchguard - burner fails to ignite or b lost flame sense 4 times in one heating cycle" according to the diagnostic codes. To correct this problem I simply turn off the Emergency Shut Off switch for a few seconds then back on and it seems to work.

I originally thought this problem only occurred with the ignition of a heating cycle, however I recently noticed that sometimes not always the furnace will go into "Watchguard" mode in the middle of a heat cycle before the desired temperature is reached. I cannot find a pattern as to when it "stops" working after working for a while. Also they would monitor the voltage to the gas valve. I dont know if the click you hear when the gas valve energizes is the valve or a click from the control board.

Looks like these units are very inteisive on sensors and readouts. Plus the boards in many of these units, depending on your model, have been recalled at least once for this or that. There is some useful info around the net if you run a search for the same thing you asked here. Most will suggest you try a cheap blue filter instead of some of the nice little extremely low flow filter all your allergens type filters which really don't do much in my opinion but tap your checkbook.

There is also some comments regarding the flame sensor having some build up and not relaying the flame is strong enough which sends the unit into watchguard. There's also alot of useful tidbits regarding the flame sensor in various gas units. Below is a link you can cut and paste to show you what I'm talking about. If you can gain access to the burner chamber and find this sensor, it may just be built up or need replacing.

furnace lost flame sense

Since your talking about it trying to ignite several times, and often failing mid heat, it's more then likely this guy at fault. A cleaning or replacement will probably get you going again. Observe the fella in this link sanding the sensor lightly on the prod end to clean and remove build-up. Gas, especially propane does a number on metal over time. That's why gas grills rarely make it past a few years before they are being completely rebuilt.

Chances are it's worn the sensor some. I'd try this before spending a fortune to call someone out. However, please make sure to take caution, disable all power, and gas inputs to the furnace before investigating.

Also, allow some time for any residual gas fumes to clear before getting in there. Hi, Joe, My furnace has the exactly same problem. Did you fix it? Thanks, John. Joe B. This is the sequence of operation when it does NOT ignite: Thermostat calls for heat operation, and the blower fan starts. What can be the problem and how can I correct it? Answer Save. Mitch Lv 5. The Big Guy. Hope this gets you started. Still have questions?If the flame sensor is bent or warped, you can obtain a new one directly from Lennox or from an appliance parts store.

Do not use sandpaper to clean the flame sensor rod. Cleaning the flame sensor with sandpaper can make it more difficult for the component to successfully sense the flame.

Lennox gas furnaces contain an important safety component known as a flame sensor. As long as the component senses the flame, it sends a message to the main furnace control board telling it to keep the main burner on and the gas valve open.

If the flame sensor can't sense the flame because it's too dirty, the furnace may shut itself off. Finding and cleaning the flame sensor in a Lennox furnace is a simple repair that takes just minutes. Flip the circuit breaker switch that corresponds to your Lennox furnace to the "Off" position. Lift the access panel on the front of the furnace straight up to clear the tabs on the bottom of the furnace cabinet. Set the remove panel aside.

Note that some Lennox furnace models require you to remove two side screws to free the front access panel. Look for a thin metal rod on the left side of the burner assembly; this is the flame sensor. Remove the screw that holds the flame sensor rod in place.

How To Test A Furnace Flame Sensor

Scrub the flame sensor with steel wool to remove any grimy build-up. Wipe the sensor with a clean tissue before replacing it to remove any remaining residue. Replace the front access panel. Flip the corresponding circuit breaker switch back to the "On" position to restore power to the furnace. Megan Mattingly-Arthur has been writing professionally since Hunker may earn compensation through affiliate links in this story. Tip If the flame sensor is bent or warped, you can obtain a new one directly from Lennox or from an appliance parts store.

Warning Do not use sandpaper to clean the flame sensor rod.

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Step 1 Flip the circuit breaker switch that corresponds to your Lennox furnace to the "Off" position. Step 2 Lift the access panel on the front of the furnace straight up to clear the tabs on the bottom of the furnace cabinet.

Step 3 Look for a thin metal rod on the left side of the burner assembly; this is the flame sensor. Step 4 Scrub the flame sensor with steel wool to remove any grimy build-up.

Step 5 Replace the front access panel. Share this article. Megan Mattingly-Arthur. Show Comments.Forgot your Password? We welcome your comments and suggestions. All information is provided "AS IS. All rights reserved. You may freely link to this site, and use it for non-commercial use subject to our terms of use.

View our Privacy Policy here. Toggle navigation Cancel. Log in. Remember Me? Login with Facebook Log in. Forgot Password? New Posts. Today's Posts. Community Member List. Forum Actions Mark Forums Read. Quick Links View Forum Leaders. Lennox Furnance going into Watchguard Mode! Thread Tools. It is about 4 years old. I am experiencing an intermittent problem with my furnace ugh!

Most of the time the furnace will operate normally, however, about 2 times per day, the furnace will enter into the Watchguard mode and shut itself off for 60 mins.

Upon returning from the 60 minute shutdown period, the furnace will operate normally. Here is how it gets to the Watchguard mode: 1 Thermostat calls for heat 2 Combustion Air Inducer turns on 3 delay 4 gas valve opens and ignitor lights flame 5 flame stays light for a few seconds, then gas valve closes no more flame 6 delay 7 gas valve opens again and ignitor lights flame, 8 flame stays light for a few seconds, then gas valve closes no more flame I know it is entering the watchguard mode because I translated the status LEDs and timed until it returned to operation.

I checked the primary limit switch, closed I checked the flame rollout switches, both closed I haven't tried to clean the flame sensor yet or checked the pressure switches.

My air filter is clean and I always replace it every 3 months. What baffles me the most is that this problem is intermittent and does not happen consistently.

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Can anyone help me troubleshoot this? I am really close to calling someone who knows what they are doing, I just don't want to pay a lot of money for something simple I appreciate any feedback!Skip to main content Flame Sensor for Furnace.

In stock. This is a flame sensor. It senses the flame of my gas furnace. The original one was over 20 years old. It stopped working so I had to get this new one. Even though my furnace is not a Goodman, it uses this same part. Add to cart.

furnace lost flame sense

In stock on April 20, Only 13 left in stock - order soon. Had flash code 2 - no flame lockout. Extended the life of old sensor by cleaning the electrode with steel wool when waiting for the new one. Replacing it with his one is a more permanent repair. In Stock. So the Carrier furnaces sometimes go through these during the heating season. I've had problems before, and cleaned the sensors late at night in the winter to get the heat working again furnace won't start when one of these fails or needs to be cleaned.

I ordered one of these as a back up to keep in the house. It helps me sleep better. Ferguson Industries F Sensor.

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Only 19 left in stock - order soon. The old flame sensor was getting unreliable, swapped out with this one and it's worked perfectly since.Modern gas- or oil-fired furnaces have several safety sensors that check on furnace operation. The furnace controller monitors these sensors constantly.

If one of the sensors reports an unsafe condition, the furnace controller shuts off fuel and power to prevent unsafe operation. This condition is known as lock out. Your furnace normally will remain in the locked-out state until you manually reset it. Most furnace lock outs are caused by problems with igniters, flame sensors and limit switches. Common causes of furnace lock outs are a defective igniter or defective flame sensor. When the furnace attempts to start, sensors check for igniter action and for the presence of flame.

If the igniter doesn't activate within a few seconds, the furnace controller stops the ignition sequence. In most furnace models, the controller will retry the ignition sequence twice more before going into lock out. If the igniter does activate but the flame sensor doesn't report the presence of flame within a few seconds, the furnace stops the ignition sequence.

It will try twice more for ignition but if the flame sensor doesn't report flame, the furnace goes into lock out. Gas furnaces with pilot lights will go into lock out if the pilot light goes out or if the pilot light fails to light up the main burner. Furnaces also include limit switches that monitor fuel pressure and the internal temperatures of the heat exchanger.

If fuel pressure is too low, or if the temperature in the heat exchanger is too high, the switch closes. This tells the furnace to shut down and go into lock out mode.

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Sometimes a dirty air filter can reduce air flow through the furnace to a point where the heat exchanger limit switch trips. Many furnaces with electronic controls will have status code lights that can tell you what caused the furnace to lock out. Once you have identified and corrected the cause of your furnace lock out, you must manually reset the furnace. Most gas furnaces can be reset by shutting off the electric power, waiting 20 seconds and turning the power back on.

Some furnace controllers will unlock after an hour or two and will try to operate again. Most oil-burning furnaces have a reset button on the burner that you press to restart the furnace.

furnace lost flame sense

If your gas furnace has a pilot light, you must relight it according to the manufacturer's directions. This should unlock the furnace. Herb Kirchhoff has more than three decades of hands-on experience as an avid garden hobbyist and home handyman.

furnace lost flame sense

Since retiring from the news business inKirchhoff takes care of a acre rural Michigan lakefront property and applies his experience to his vegetable and flower gardens and home repair and renovation projects. By Herb Kirchhoff. Hunker may earn compensation through affiliate links in this story.During these challenging times, we guarantee we will work tirelessly to support you.

cfm Tech Tips – Troubleshooting Furnace Control Boards — Faults & Flashes

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We will get through this together. Is your furnace having trouble staying on once it fires up? Does it quickly shut off, after you start it?

Does it do this a few times and then fully shuts down? Many homeowners have this problem every year because of a dirty flame sensor. Heating, Ventilation, and Air Conditioning is a complex industry, but this repair is simple enough that you can perform by yourself. In our example will show a gas-fired furnace, but you can find flame sensors in boilers and other gas-burning appliances.

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This article has also been viewed 34, times. Learn more Explore this Article Steps. Tips and Warnings. Things You'll Need. Related Articles. To avoid danger, it is very important to shut off the power to your furnace or any other applianceprior to making any repairs. There will usually be a light switch toggle switch on or near your furnace. If this switch is not present, furnaces have a dedicated breaker; locate your furnace breaker and shut your unit down. NOTE: Turning off the thermostat does not shut down the power to your unit.

Also, there are many different types of furnaces and appliances; if your gas valve is not electrically controlled, you will need to shut off the gas to the unit as well.

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Should you be confused about any of the information provided here, because it does not match with what you see on your unit, STOP!