Furnace will not heat.

I would buy another board. The boards contain safety features.

Troubleshoot an ignition problem on a Lennox gas furnace ...

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https://www.youtube.com/watch?v=yXIxgzwMkPs
Nov 17, 2012 - Uploaded by grayfurnaceman
This furnace should light its pilot with a spark then the pilot proves its on ... Troubleshoot an ignition problem on a Lennox gasfurnace .... Pilot and no inducer but is the same model as that great video! ... You probably have dirty burners. ... How do you know spark module is not sending 24 volts to mv and pv ...

Lennox Furnace Model G11Q3-82-2 - RepairClinic.com

Sounds like the blower motor is getting hot and cycling on internal motor overload. Probably airflow or the blower bearing or capacitor. Turn off all power to the unit then you need to check the filter, Evaporator coil to see if air is getting through it. When checking the coil for a blockage you need to remove a side plate, it's triangular and check the entering air side of the coil to see if its blocked. You need a volt ohm meter with a micro-farad scale to check the blower capacitor and motor amps. You could have a bad motor bearing.

No probably 12 years old and keeps going out purchase the module

I would suggest that you have someone turn thermostat up to call for heat while you are watching. Being that old it may or may not have a induced draft motor on it. It it does the draft blower should come on first, then spark igniter,then pilot ,next the main burner,and after a short period the main blower. If you do not have induced draft motor the spark igniter should come on as soon as thermostat calls for heat. If it doesn't I would check all electrical connections making sure they are all clean and tight fitting. Just follow it through step by step . You can use volt meter to check across red and white wires from thermostat to where they hook into furnace. When you are calling for heat you should read about 24 volts. I would be inclined to replace spark igniter but if it does what it's is suppose to then I would go to gas valve. It might be worth your time to check connections on t-stat. I have occasionally seen wires that were broke under screw and some time make connection and other times not. You can also remove red and white wires from t-stat and temporairly touch them together. this should turn heater on. Hope this helps. Thanks.

Hello,See if it is blowing out.Relite the pilot and run the fan(blower) with out the main burner running.A cracked heat extanger will be the cause if it blows out.

Tie red and white wires together after removing thermostat from wall, if unit comes on replace thermostat, if not check limit controls for continuity, Good luck.

Hi,
You have a pretty old Lennox there. The G-10's went out of production many years ago....
Since you have pilot and the thermocouple was replaced you will need to check and see if there is voltage going to the gas valve. You should have 24v AC across the two wires on the gas valve when there is a call for heat. If not then the limit switch or the high limit switch are cutting the power to the gas valve. You will need to reset or replace them.
If you have power to the gas valve then you have a
faulty gas valve and will need to replace that.
It if very possible that the gas valve has failed on a furnace the age of yours. That would be my first guess. But do check for voltage before replacing it.

I hope that this will help you to solve your problem!

Thanks for using Fixya!!

Heatman101

The bearings are bad. You need to replace the motor. Motor cost $75 to $125. Labor is on avg. $150 to $400 with an decent A/C Company . You can try to oil it but its not recommend by Lennox. That furnace at the time they build it was top of the line. Good Luck.

If the burners do not fully ignite, the sensor will shut the furnace down. The lack of sufficient burner flame is a gas valve or gas pressure problem within the valve.
Replacing the gas valve with the original one may get you going. I surely suggest a professional service company for safety reasons and a thorough inspection. A 20 year old furnace is past it's normal life span.