Gas and Oil Home Heating Furnaces - Lennox Problems

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clarkclan
12-21-08, 11:19 AM
I have a Lennox Diplomat 80mgf3/4-100A-1. The burners light for only a few seconds and then shuts down. (no matter where the TS is set). every 3-4 minutes.
The house isn't cold, so I know that the burners are staying on some of the time. During all this the blowers are blowing cold air. Is this normal? I have no manual or any experience with this system. Could you point me in the right direction..I don't want to just purchasing parts till the problem is gone...


Pulpo
12-22-08, 05:54 PM
I would jump the thermostat to see if it continues to run and as always, check the filter.

Skip4661
12-22-08, 06:03 PM
The flame sensor is dirty. The flame sensor sits in front of one of the end burners. The ignitor/sparker is on one side of the burners the flame sensor is on the opposite side. You need to remove this sensor and polish it with steel wool or emery cloth, a scotchbrite pade will work in a pinch. Sometimes it requires a little dis-assembly.


clarkclan
12-23-08, 10:14 AM
Cleaned the flame sensors, still a problem..How can I tell If it is the GAS VALVE or the RAM CARD. No diagnostic codes ever show?

Skip4661
12-23-08, 10:46 AM
If the burners light it's not the gas valve. Do the burners light from one side to the other without any delay? If they don't light evenly and smooth you you need to remove the burners and blow them out with air.

clarkclan
12-23-08, 12:28 PM
The burners light evenly. Now the igniter is trying to light the burners but every few attempts they dont light....Do gas valves fail intermittantly or does this point to the RAM CARD...

clarkclan
12-23-08, 12:41 PM
The burners light evenly. Now the igniter is trying to light the burners but every few attempts they dont light....Do gas valves fail intermittantly or does this point to the RAM CARD...

Skip4661
12-23-08, 04:56 PM
Yes, gas valves can have intermittent problems. I wouldn't replace anything without cleaning the burners first. Do you hear gas hissing when it doesn't light.

clarkclan
12-24-08, 10:25 AM
No gas hissing when it doesn't light.

clarkclan
12-24-08, 11:05 AM
Can you tell me what the power requirements are to open the gas valve and the amps I sould be seeing for the flame sensor...Thanks and Merry Christmas...

ecman51`
12-24-08, 12:21 PM
Now the igniter is trying to light the burners but every few attempts they dont light

Then you don't have to worry about the flame sensor being the culprit if this is the case.

Do you have a hot surface ignitor (HSI) glow coil that lights the burners?