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gnt
9 Posts |
 Posted - 02/04/2010 : 4:23:27 PM
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| I have a G26 Model furnace. It will run and bring the house up to temperature and stop, but when the temperature goes down, it will not start back up unless the thermostat gets turned down and back up or shut off then back on. Then it will heat for one sometimes two cycles then you have to shut it off again. I have replaced the thermostat and still have the same problem. Do I need a new BCC board or is there something I am overlooking? Thanks for any help! |
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Cozy.Support
4620 Posts |
Posted - 02/04/2010 : 4:51:18 PM
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What is the model number? There was two types of control systems used on this model series that were totally different from each other... a complete model number would be a good place to start.
CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.
Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
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gnt
9 Posts |
Posted - 02/04/2010 : 4:55:08 PM
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| Model number is G26Q3/4-100-2 |
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MechAcc
1277 Posts |
Posted - 02/04/2010 : 11:29:45 PM
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What voltage checks have you done?
I am not an employee of CozyParts. The opinions that I post are my own.
Please have your furnace inspected annually by a qualified service technician. Have all of your fossil fuel appliances tested annually for carbon monoxide production by a professional.
Get a good Carbon Monoxide Alarm. Replace it according to manufacturers recommendations usually every 3-5 years. CO concerns are not just for the winter but 24-7. UL approved alarms alarm high. For a low level alarm do a search for CO Experts or NSI 3000 a low level CO monitor. |
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gnt
9 Posts |
Posted - 02/05/2010 : 09:07:06 AM
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| I have only checked the voltage from the thermostat. I am getting 26 VAC |
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MechAcc
1277 Posts |
Posted - 02/05/2010 : 5:21:29 PM
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You need to check voltage at ignition control. If this a blue box labeled Johnson Controls it is most likely that control. Before you order a replacement have the heat exchanger inspected.
I am not an employee of CozyParts. The opinions that I post are my own.
Please have your furnace inspected annually by a qualified service technician. Have all of your fossil fuel appliances tested annually for carbon monoxide production by a professional.
Get a good Carbon Monoxide Alarm. Replace it according to manufacturers recommendations usually every 3-5 years. CO concerns are not just for the winter but 24-7. UL approved alarms alarm high. For a low level alarm do a search for CO Experts or NSI 3000 a low level CO monitor. |
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gnt
9 Posts |
Posted - 02/06/2010 : 11:29:53 AM
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| Okay. Ignition control is getting voltage when the draft motor starts and engages the pressure safety switch. Problem is, the draft motor does not always start when calling for heat. I know that if the switch gets stuck open or closed it will not run. I have checked the resistance on the switch and it appears to be ok. I am wondering if the contacts are going bad or the diaphragm may be worn. Is there a way to check this to verify without replacing the pressure switch? |
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Cozy.Support
4620 Posts |
Posted - 02/06/2010 : 11:40:03 AM
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Check the voltage going to the induced draft blower while the blower is supposed to be running. This is going to lead you to an answer faster than ohming the switch.
CozyParts.com, Inc. is an Independent Lennox Dealer providing a national parts distribution resource for Lennox parts since 2002. The Cozy.Support team does not provide a diagnosis for users of this forum. We do, however, try to provide information that will help servicers arrive at their own diagnosis.
Once you know what part you need, you can contact the Cozy parts department by using the link below
http://www.cozyparts.com/Lennox-Parts/locator_form.aspx
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gnt
9 Posts |
Posted - 02/06/2010 : 11:42:59 AM
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| the voltage going to the induced draft motor is 0 vac. When it is running it is 120vac |
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gnt
9 Posts |
Posted - 02/06/2010 : 11:46:28 AM
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| I mean it is getting 0 vac when the thermostat is calling for heat. |
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gnt
9 Posts |
Posted - 02/07/2010 : 08:21:25 AM
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| Okay, when the thermostat is calling for heat, I am getting a 24vac signal, I have checked the primary limit switch(closed) and the flame rollout switch(closed) but there is no output signal to the induced draft blower motor. I still have to turn the unit off and back on to get the furnace to run. |
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gnt
9 Posts |
Posted - 02/07/2010 : 08:33:41 AM
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| And the air pressure switch is open |
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slctech
1097 Posts |
Posted - 02/07/2010 : 10:01:38 AM
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So what your trying to say, is that intermittently the inducer motor fails to operate even when you have a call for heat?
You have verified that the thermostat is calling for heat by measuring approx 24v across W and C at the terminals on the furnace?
If 24v across W and C IS present and inducer is NOT operating then measure voltage to inducer motor, should be approx 120v.
If you still have NO voltage to inducer motor and there is 24v across W and C on the terminal board, then it is the board or loose wiring between the board and inducer motor.
If you DO have voltage at the inducer and it is not operating, then most likely a faulty inducer motor and best to replace the entire inducer assembly.
If all along you have a call for heat at the thermostat, but NO voltage readings across W and C, then need to check out thermostat, thermostat wiring, and connections.
As a Lennox Technician I feel basic repairs and maintenance can be performed by the homeowner. But I highly suggest that periodic maintenance should be made by a certified licensed technician. You should contact your local Lennox technician for any repairs or issues that are outside your comfort zone. Property damage, personal injury, and death can occur from improperly repaired or maintained systems. Replacing a part doesn't always resolve the issue that caused the part to fail! |
Edited by - slctech on 02/08/2010 11:09:51 PM |
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gnt
9 Posts |
Posted - 02/08/2010 : 7:58:35 PM
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| Thank you. After checking everything I discovered the relay for the combustion motor is going bad. If I tapped the relay on the bcc board, the motor would start, then stop. I replaced the bcc board and furnace is running just like it should. Thanks again for all of your help. |
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