It starts for about 2 seconds, then starts again for about 2 seconds, then shuts off. After about the 3rd time it tries to start, the furnace makes a thump sound and blower kicks in and runs for about 15-20 seconds and then completely stops.
First let me thank all the pros that take the time to answer our questions. My wife thinks I'm a genious. I had the same problem up to 30 minutes ago and fixed it from a solution found on a different webpage. There's sensor sticking up where the flames come out with a single wire coming from it. Remove the sensor and scrub it with steel wool. Replace it and get your hummer from the old lady because you just saved her a few hundred bucks.
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Re: My Lennox Furnace starts and stops.
The reason why it stops and starts is that the sensor within the burner can not sense a flame in the furnace. The parts need to checked is the fuel filter, Air in the line, burnt out arcing rods or a bad ac high voltage transformer.
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Nov 17, 2012 - Uploaded by grayfurnaceman
This furnace should light its pilot with a spark then the pilot proves its on ... Troubleshoot an ignition problem on a Lennox gasfurnace .... Pilot and no inducer but is the same model as that great video! ... You probably have dirty burners. ... How do you know spark module is not sending 24 volts to mv and pv ...
Problem: Your furnace will not ignite the gas to
produce heat for your home. When a furnace has a bad ignitor what I see most of
the time is the following sequence of operation:
Thermostat calls for heat.
Draft inducer motor starts.
Pressure switch attached by a small plastic or rubber tube senses the
negative pressure produced by the draft inducer and
Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small
metal probe about 1/8" in diameter, with a white
porcelain base) does not sense the flame, so after 8
to 10 seconds the hissing sounds stops with no
ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back
off and on again. Then the sequence starts all over
again with no ignition of the gas.
Solution:You probably need to
purchase and install a new ignitor. I would suggest that you inspect your
ignitor closely for cracks. Make sure you do not
touch the ignitor with your bare hands. If you do not
visually see a crack, then you could have a furnace control board problem or a
limit, rollout switch problem. The furnace's control board
might not be supplying the voltage to the ignitor.If your furnace
lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then
you need to clean your flame sensor with light sand paper or steel wool. You
might need a new flame sensor, but most of the time they can be cleaned an will
work well after cleaning.
you will need to verify voltage from the board to the inducer. If you have the installtion manual there is a flow chart for the sequence of operation of the furnace.
The basic sequence is:
1. thermostat calls for heat
2. inducer motor starts and runs for a pre-set amount of time
3. the pressure switch closes and allows for ignition trial
4. ignition is proved back to the board allowing the system to operate.
Verify 120VAC to the inducer motor upon call for heat from stat, if you have 120 at the leads that connect to the inducer and it does not start , the motor is faulty. If the inducer starts use a voltmeter across the pressure switch terminals, a voltage reading of 0 VAC will verify contact closure and ignition should occur.
The pulse furnace was under a factory recall due to breaches in the heat exchanger, unfortunately for you, the Lennox Corp. has ended the program that allowed for an allowance / furnace for replacement. To test the heat exchanger a special kit is required from lennox that will verify integrity of the heat exchanger. (If the heat exchanger seal has been comrimised the pressure switch will not prove and the igniton sequence will be interupted and cause the system to go into "lock-out" mode).I know this is probably not what you wanted to hear. Hope this helps, please list as "very helpful" if it did
Sounds like a dirty flame sensor.
Also 9 degrees is a large swing to recover. Most specialist will advise no more than a 5 degree set back, otherwise recovery time eliminates any savings you may achieve.
You can sand the flame sensor but it sounds like another problem. Sounds like a limit switch or something in the control circuit, You need to have a service tech look at this. Ask for free estimate on repair. I have worked on hundreds of these units and they are sometimes tricky to work on. Lenox has come up with new controls for the whisper heat furnace to replace the old ones. If the flame sensor is bad the unit will try to light a few times and lock out and you ahve to kull power to the furnace to reset. If this is whats happening clean the sensor nd you should be ok If not you need help from a service tech.Rus
The bearings are bad. You need to replace the motor. Motor cost $75 to $125. Labor is on avg. $150 to $400 with an decent A/C Company . You can try to oil it but its not recommend by Lennox. That furnace at the time they build it was top of the line. Good Luck.
Try to locate the red and white wires either behind your thermostat or on the furnace itself. Jump them out and see if the furnace stays on. If you do it at the furnace you will need to hold the door switch down. If it runs fine, you have found your problem (the thermostat) if it goes out again, the furnace will display a number of blinks on the circuit board. Look on the reverse side of the furnace access door and there should be an Error Code chart to get you started figuring where to look next.