Gas and Oil Home Heating Furnaces - Lennox G50 furnace help
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jshobert2002
11-01-09, 01:23 PM
My Lennox heater comes on intermittently. I know nothing about heaters. A friend said it’s the control board. I don’t know but want to try to fix it without paying someone to come out and replace something I could do myself. I really need some help, thank you in advance.
SeattlePioneer
11-01-09, 01:31 PM
A furnace doesn't just turn on.
It goes through a series of events that eventually result in heat being circulated through the dwelling space if everything works properly.
If it doesn't work properly, it stops at one of those events.
Your task is to identify how far along tyour furnace gets with that sequence of operation.
Take the front cover off the furnace so you can see the burner compartment.
Carefully observe what happens when you turn the thermostat up to call for heat. You might need to do that several times to catch the various details.
Report back on what you found.
It goes through a series of events that eventually result in heat being circulated through the dwelling space if everything works properly.
If it doesn't work properly, it stops at one of those events.
Your task is to identify how far along tyour furnace gets with that sequence of operation.
Take the front cover off the furnace so you can see the burner compartment.
Carefully observe what happens when you turn the thermostat up to call for heat. You might need to do that several times to catch the various details.
Report back on what you found.
jshobert2002
11-01-09, 04:08 PM
When it works, the igniter heats up, can hear gas start, then the igniter lights the gas. The last time it did that, I put the panel back on and walked out of the hall. A few minutes later I came back and pulled the panel back off and it wasn't on.
When it doesn't work (which is most of the time.) I can hear the click from the thermostat then nothing happens. The bottom panel has the lights (red and green) which are supposed to indicate problems. They flash alternately one then the other fairly quickly.
When it doesn't work (which is most of the time.) I can hear the click from the thermostat then nothing happens. The bottom panel has the lights (red and green) which are supposed to indicate problems. They flash alternately one then the other fairly quickly.
GRIMKNOTME
11-02-09, 06:01 PM
Turn panel around and read code ....should have a code chart on it.........................
SeattlePioneer
11-02-09, 06:33 PM
I'm guessing that the limit switch is opening, but you should check that with an AC voltmeter.
Things that impair the airflow through the furnace cause the limit switch to open, such as a plugged furnace filter, return air vent covered over, too many warm air vents closed and other such things.
Seattle Pioneer
Things that impair the airflow through the furnace cause the limit switch to open, such as a plugged furnace filter, return air vent covered over, too many warm air vents closed and other such things.
Seattle Pioneer
jshobert2002
11-04-09, 08:24 AM
Turn panel around and read code ....should have a code chart on it.........................
the code says:
The following conditions are sensed during the ignitor warm-up period only:
1) improper main ground;
2) broken ignitor; OR; Open ignitor circuit;
3) Line voltage below 75 volts.
i don't know hardly anything about this stuff. i can't tell if the ignitor is broken and don't know how to tell if i have an open ignitor circuit
the code says:
The following conditions are sensed during the ignitor warm-up period only:
1) improper main ground;
2) broken ignitor; OR; Open ignitor circuit;
3) Line voltage below 75 volts.
i don't know hardly anything about this stuff. i can't tell if the ignitor is broken and don't know how to tell if i have an open ignitor circuit
jshobert2002
11-04-09, 08:35 AM
I'm guessing that the limit switch is opening, but you should check that with an AC voltmeter.
Things that impair the airflow through the furnace cause the limit switch to open, such as a plugged furnace filter, return air vent covered over, too many warm air vents closed and other such things.
Seattle Pioneer
where would the liimit switch be located?
Things that impair the airflow through the furnace cause the limit switch to open, such as a plugged furnace filter, return air vent covered over, too many warm air vents closed and other such things.
Seattle Pioneer
where would the liimit switch be located?
ecman51`
11-04-09, 08:45 PM
Do you have a multimeter to test with?
Ignitors often slowly deteriorate, across some area of it, before they actually burn through. In the process, the resistance goes up, and the heat generated by the HSI drops. It gets to the marginal stage where one minute it might work and the next minute it don't.
But - a marginal HSI, if it lights the burner, will NOT then make the burners to go out, unless either yourr HSI doubles as a flame sensor -or -this is not even the issue at all - or -there are 2 issues simultaneously.
How can you tell if you have a separate flame sensor not as part of the HSI? Look and see if you have one lone skinny wire that heads in towards the combusion chamber. If you do, that be it. If not, the HSI just may be the flame sensor also.
Ignitors often slowly deteriorate, across some area of it, before they actually burn through. In the process, the resistance goes up, and the heat generated by the HSI drops. It gets to the marginal stage where one minute it might work and the next minute it don't.
But - a marginal HSI, if it lights the burner, will NOT then make the burners to go out, unless either yourr HSI doubles as a flame sensor -or -this is not even the issue at all - or -there are 2 issues simultaneously.
How can you tell if you have a separate flame sensor not as part of the HSI? Look and see if you have one lone skinny wire that heads in towards the combusion chamber. If you do, that be it. If not, the HSI just may be the flame sensor also.
GRIMKNOTME
11-05-09, 06:05 AM
the code says:
The following conditions are sensed during the ignitor warm-up period only:
1) improper main ground;
2) broken ignitor; OR; Open ignitor circuit;
3) Line voltage below 75 volts.
i don't know hardly anything about this stuff. i can't tell if the ignitor is broken and don't know how to tell if i have an open ignitor circuit
I think you have a glo-stick on your right burner bar , does it glo ?
Does all 3 or 4 burners light in a quick sequence ?
Does all of them light , how long do they stay lite ?
You have a flame sensor located to the very far left sticking down into last burner to make sure all burners light
And that limit is located above the flame sensor , should be black with 2 screws holding it in with 2 wires plugged into it , POWER OFF , you can gently remove these two wires clean with sand paper spade connectors and terminals.
1) improper main ground;
You gotta have a good ground , where your main 120 volt wire comes in , WITH POWER OFF , you can run an additional ground to a copper water pipe preferably , or gas pipe away from furnace with a ground clamp.
3) Line voltage below 75 volts.
Takes round 120 volts of course you can ck this at incoming power to furnace
The following conditions are sensed during the ignitor warm-up period only:
1) improper main ground;
2) broken ignitor; OR; Open ignitor circuit;
3) Line voltage below 75 volts.
i don't know hardly anything about this stuff. i can't tell if the ignitor is broken and don't know how to tell if i have an open ignitor circuit
I think you have a glo-stick on your right burner bar , does it glo ?
Does all 3 or 4 burners light in a quick sequence ?
Does all of them light , how long do they stay lite ?
You have a flame sensor located to the very far left sticking down into last burner to make sure all burners light
And that limit is located above the flame sensor , should be black with 2 screws holding it in with 2 wires plugged into it , POWER OFF , you can gently remove these two wires clean with sand paper spade connectors and terminals.
1) improper main ground;
You gotta have a good ground , where your main 120 volt wire comes in , WITH POWER OFF , you can run an additional ground to a copper water pipe preferably , or gas pipe away from furnace with a ground clamp.
3) Line voltage below 75 volts.
Takes round 120 volts of course you can ck this at incoming power to furnace
jshobert2002
11-06-09, 07:04 PM
I think you have a glo-stick on your right burner bar , does it glo ?
Does all 3 or 4 burners light in a quick sequence ?
Does all of them light , how long do they stay lite ?
You have a flame sensor located to the very far left sticking down into last burner to make sure all burners light
And that limit is located above the flame sensor , should be black with 2 screws holding it in with 2 wires plugged into it , POWER OFF , you can gently remove these two wires clean with sand paper spade connectors and terminals.
1) improper main ground;
You gotta have a good ground , where your main 120 volt wire comes in , WITH POWER OFF , you can run an additional ground to a copper water pipe preferably , or gas pipe away from furnace with a ground clamp.
3) Line voltage below 75 volts.
Takes round 120 volts of course you can ck this at incoming power to furnace
i was able to check the igniter with a voltage meter. i jumps to 130-134 for a split second then sits at 102 v. if the igniter is unplug the heater fan will turn on for a second. with the ignitor pluged in the fan never starts.
Does all 3 or 4 burners light in a quick sequence ?
Does all of them light , how long do they stay lite ?
You have a flame sensor located to the very far left sticking down into last burner to make sure all burners light
And that limit is located above the flame sensor , should be black with 2 screws holding it in with 2 wires plugged into it , POWER OFF , you can gently remove these two wires clean with sand paper spade connectors and terminals.
1) improper main ground;
You gotta have a good ground , where your main 120 volt wire comes in , WITH POWER OFF , you can run an additional ground to a copper water pipe preferably , or gas pipe away from furnace with a ground clamp.
3) Line voltage below 75 volts.
Takes round 120 volts of course you can ck this at incoming power to furnace
i was able to check the igniter with a voltage meter. i jumps to 130-134 for a split second then sits at 102 v. if the igniter is unplug the heater fan will turn on for a second. with the ignitor pluged in the fan never starts.
jshobert2002
11-06-09, 07:08 PM
i do have a seperate flame sensor on the left of the gas nosles. i was able to check the igniter with a voltage meter. i jumps to 130-134 for a split second then sits at 102 v. if the igniter is unplug the heater fan will turn on for a second. with the ignitor pluged in the fan never starts.
GRIMKNOTME
11-07-09, 06:51 AM
You have a flame sensor located to the very far left sticking down into last burner to make sure all burners light
And that limit is located above the flame sensor , should be black with 2 screws holding it in with 2 wires plugged into it , POWER OFF , you can gently remove these two wires clean with sand paper spade connectors and terminals.
Did you do these,are you sure glo-stick is glownig each time , and gas valve is opening each time.
Take some time to turn heat on , run 10 minutes lower t-stat till fan stops ,repeat , do this when you got time to spend ( list any thing that does not work )
And that limit is located above the flame sensor , should be black with 2 screws holding it in with 2 wires plugged into it , POWER OFF , you can gently remove these two wires clean with sand paper spade connectors and terminals.
Did you do these,are you sure glo-stick is glownig each time , and gas valve is opening each time.
Take some time to turn heat on , run 10 minutes lower t-stat till fan stops ,repeat , do this when you got time to spend ( list any thing that does not work )