LENNOX control board WATCHGUARD problem - http://www.hvacmechanic.com/ Forums
Original message
| tony
 |  "LENNOX control board WATCHGUARD problem"
, posted Sun 9 Nov 23:09  
Hi,
I have 8 year-old LENNOX 80MGF-2, with EGC-1 BURNER/IGNITION/BLOWER CONTROL BOARD. Everytime when I turn on either thermostat panel power or the furnace electrical power, the burner works fine, and room temp. goes up until the setting value(let's say 21 degC), the furnace stops, but diagnostic code shows WATCHGUARD MODE.
The probelm is the next cycle. The room temp. drops down(thermal still displays the setting temp., like 21 deg C, I think there is tolerance), and thermostat is actived to trun on the blower, then ignition trial, but not flame(Burner don't work!), ignition tries three times, and system lockout,blower stops a couple minutes later. The diagnostic code shows the WATCHGUARD, two LED flashing alternately, burners have failed to ignite. The thermostat panel shows HEAT ON.
The funny thing is when the the room temp. keeps dropping down until to 20 deg, which is different from the setting value, the furnace work fine, LEDs fast flashing.After temp. goes back to the setting, burner stops and LED shows WATCHGUARD" again.
I am just wondering this is normal operation of the LENNOX80MGF?
I clean the flame sensor like Xenos' suggestion to Cheri today,but I used soft paper. Nothing improved. LEDsflashing alternatelt, and burner shut off, then several ignition trials, furnace stops.
Thanks for any comments.
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Replies:
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| Xenos
Webmaster 
| "Re(1):LENNOX control board WATCHGUARD problem" , posted Mon 10 Nov 17:52
Hi Tony thanks for the details. Some of the operation may be normal others are not.
First when ever there is a call for heat the Led will flash faster ,if a lockout occurs the board will reset it’s self in 60 minutes. This may be this temperature difference thing. Now there is a problem as to why your going off on flame failure in the first place. The biggest problem I see it that you never see the burners fire when it’s failing. Email me at xenos@hvacmechanic.com and I will reply with the service manual you may read something in it that can lead us in a direction.
Xenos.
The best way to escape a problem is to solve it.
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| | tony
| "Re(2):LENNOX control board WATCHGUARD problem" , posted Tue 11 Nov 21:58:
thanks for the manual.
section of "furnace control (A3)" on Page 7 gives me more clues.
After I clear all errors by either turning off the power to unit or shorting the jumper on board, furnce warms up following the thermostat's call. When thermosta turns off the heat demand,the burner shuts off as expected, but LEDs flash fast like there is still heat call demand( something wrong here), then ignition tries several time, unit lockout for a long time period( longer then 60 minutes). Later on, furnace starts again, and repeats the same pattern.
It looks like furnace has been set to run every certain period due to the lockout.
[this message was edited by tony on Tue 11 Nov 23:05] |
| | Xenos
Webmaster
| "Re(3):LENNOX control board WATCHGUARD problem" , posted Wed 12 Nov 08:37
From the explanation you give it sounds like the board is messed up. I would recommend calling in a Lennox Tec at this point to verify it’s operation.
Xenos.
The best way to escape a problem is to solve it.
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| | tony
| "Re(4):LENNOX control board WATCHGUARD problem" , posted Wed 12 Nov 12:09:
Agree! The board works funny. The orignal board was changed to EGC-1 last year by the service tech according to my previous owner's comment.
Thanks!
[this message was edited by tony on Wed 12 Nov 12:13] |
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