I have a lennox furnace without a pilot lite, it will glow and the flame will start and then shut off immediatly, sometimes it works fine and then it has problems. The warning lights give me a warning that it didn't sense a flame, is this a flame sensor issue?
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Re: lennox intermitent flame problem
Yes the flame sensor is not allowing the ignitor to start, you will need to remove the flame sensor, and clean the black carbon build up from the stem of the flame sensor, replace the flame sensor and turn the furnance back on, this will correct the problem.
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if furnace fires up then immediatly shuts off check the flame sensor. make sure it is sitting far enough inside the burner box and has proper continuity. if ur getting ignition failure without having furnace fire up, check proper voltage to hot surface igniter, continuity within igniter
I've got an easy way for you to check, and then we can help you from there. First pop open both lids to your furnace (this may require a screwdriver). Turn up your thermostat, push the safety interlock button in if it has one (it's a button that turns off the power when the doors are removed), and watch.
On most modern furnaces (past 20-25 years) you'll hear/see: 1. Inducer fan 2. orange glow (ignitor) 3. Gas valve opening and ignition (flames) 4. Main Fan.
that's normal heater operation. The most common issue here is a burned out ignitor, in which case you wouldn't see the orange glow but the sequence would attempt to continue anyway (the gas valve will open and hiss gas, but it won't lite, then it'll give up and try again a few minutes later).
On older furnaces there's a pilot light to start with, the click of the gas valve and boom... ignition.
On new furnaces it's Inducer fan gas valve opening spark - ignition Main fan.
and there are some oddballs in between, particularly the Lennox Pulse. If that's your furnace just back away slowly and call a professional... some guys won't even touch those, so be sure to mention what it is... if you call a pro.
So go ahead and watch it run, then tell me/us what you see.
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.
Sounds like the flame rod is not acknowledging flame. The rod stick up in the flame. Clean the rod and try again. thre could be other problems bad roll out bad limit switch or something in control circiut but start there. Rus
If you have a hot surface igniter (glow coil) it has a secondary purpose after ignition and that is to sense that there is actually flame present. If the HSI is located on one end of the burners look to the other and see if there is a small rod that protrudes in to the flame as well. If so it is part of this flame proving cycle. Take some sand cloth and clean it. This may buy some time but the rod should soon bee replaced.
I'm a little confused by your terminology. You are saying you have a pilot lite and electric heat strips? Are you possibly meaning burners? Is the heater running for 2 hours straight without shutting off? how cold is it there? Lastly what temperature do you have the thermostat set at and how close does it get to the temp. before it shuts off?