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Is it possible that a thermostat operates correct all the time except when it reaches the temperature that is set doesn't maintain that temperature?
I noticed that actually that thermostat gives a signal to the furnace but furnace doesn't turn on but that happens only when thermostat needs to maintain temperature that is set.
Is it possible that thermostat isn't working at that regime (to hold the set temperature)?
I just posted a similar problem today with the LED displays (User ID: simshawk). My unit is a Lennox Elite Surelight, 6 years old, Nat Gas, using a ritetemp thermostat.
When the desired preset is met, the unit kicks off and will not restart until I perform a manual reset.
Here is my post:
Having the following problem.
Woke this morning and temp in house was 62degs. Check thermostat and it said heating, temp set on 68.
Checked the unit and the diagnostic LEDs were flashing alternatively and slow. According to the Diag Sheet, this is "Watchguard - Burners failed to Ignite".
Shut unit down and waited 15mins, performed a restart and unit was working properly, both LEDs flashing simultaneously and slow.
Temp got to preset value 71 degress and the unit shut down again. Noticed temp went back to about 67 degrees, thermostat was showing heating, but nothing was coming from the vents, and no flame on the unit.
Check LEDs again and saw the same "Watchguard" failure as above. Shutdown unit and performed a restart, heater kicked on, but now the LEDs are #1 slow flash, and #2 fast flash, which according to the status table is "Low flame signal, check flame sensor".
Help, its going to be really cold tonite in MI.
Jerry
Clean the flame sensor, a small metal rod that is infront of one of the burners
Hi, I have the same problem as Senada, Simshak, and JS16. First my info I guess:
Lennox Whisper Heat G20
7yrs old
80% Efficiency
Forced Air furnace
NG
Digital Stat (Honeywell if it matters)
Seems like the furnace doesn't want to go through a full cycle. The stat requests heat, the furnace lights up, it works for a while, and then shuts down refusing to start until a manual off/on procedure is carried out. Sometimes it works till the desired heat is achieved, other times it just cuts out randomly as if it were bored or tired of doing its job. It dies with the damper open, and a led on the ignition control flashing rapidly.
A little history here is the furnace was doing the same thing last year so I called in a "professional" to see if he could fix it. After telling him what it was doing he put it through the paces. He removed the covers, and bypassed the safety controls then fired it up checking the pilot light, the burners, the stat etc. After an hour or more of this he finally declared " your problem is that the furnace shuts off and won't fire back up again and that little light on the board flashes off and on" .... um thanks tips. After much head scratching and a few hmmsss and ahhhs he concluded that the only possible fix would be to replace the motherboard on the furnace. A few hours and $327.17 later and the furnace worked sort of. Now instead of shutting down early the little furnace was sure to reach the desired heat and then shut off, led flashing, refusing to reignite until the manual off/on cycle was repeated. My battle with him continues but that is another story.
Now we are in back in furnace season and it has decided to shutoff as it feels again. Sometimes reaching full heat, and sometimes shutting down early, but always refusing to reignite, with that damn led flashing. I haven't noticed a regular pattern in the temp it shuts down at, but I did notice that our friend the led has learned a new trick. Now instead of flashing rapidly as if trying to emulate a strobe light, sometimes it chooses to flash at a slower rate (perhaps its getting tired from flashing so much).
I located the flame sensor you mentioned, and managed to gain access to it (sort of) by removing a panel on the damper without damaging anything. It doesn't seem to be dirty, but before I go and do something stupid, perhaps you could tell me how to clean it ie: will household cleaners hurt it or make it dirtier??, soap and water???, no water as it could corrode wire?? etc. Or is there possibly something else?? Maybe we should change the motherboard again? If that is the case I think I'll buy a new furnace, I can handle spending the $20 bucks for a new filter each year, but shelling out over $300 every year on a new motherboard is a bit much. Hope you can help, and thanks in advance.
Linear Mode
