Lennox heater just stopped working.

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Old 04-14-13, 10:10 AM
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Lennox heater just stopped working.

I apologize first of all as I have no idea about how a furnance works so forgive my ignorance. We have a Lennox Elite furnace that I noticed last night was not coming on. (We live in the Chicago area) I have attached a quick video for the furnace and of our thermostat. From what I can tell, the pilot light is not coming on and also when I switch the thermostat to "Fan On" from "Auto" nothing happens. However, when I hit a button inside the furnace (you will have to see the video..it's only about 1 1/2 minutes) it sounds like the inducer (I hope that is right) is kicking on but the pilot light is not igniting. Thanks for any help or direction. Here is the link to the video and I hope I am not violating any rules of the forum.

Lennox Heater that is not working - YouTube
 
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Old 04-14-13, 11:08 AM
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The button that you are pushing is a door switch.

Post the model number on the furnace tag. It is on the left side of the burner section.

Reinstall the lower panel so that the door switch is depressed.
Does the fan work?

Give the stat a heating demand and observe (or record) the sequence of operation and post this information.
 
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Old 04-14-13, 11:25 AM
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The model number is g23q3/4-100-4. I put the the door on and after a few seconds it ignited and seemed like is was going to work. After a couple minutes, it shut down again and the fan never turned on. Squirrel cage bad???? And thanks Houston204 for your reply..
 
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Old 04-14-13, 11:32 AM
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Does the squirrel cage spin freely when power is removed?
Do you have a meter?


 
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Old 04-14-13, 11:49 AM
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The burner ignited again and I went upstairs and switched the thermostat from "Auto" to "Fan On" and this time the fan turned on and heat is blowing. I can check the LED after the house warms up a bit... 61 degrees is a bit chilly. I am now thinking that the thermostat is not working properly. Any other suggestions Houston204? Edit...I do not have a meter...
 
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Old 04-14-13, 12:12 PM
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Replace the blower motor capacitor. A weak cap struggles to start the blower in the lower heating speed.

You can buy a meter for a little over $50 to check a cap or buy the cap for a fraction of that cost.





Match the voltage and microfarad rating of the existing cap.
A 5 microfarad (also listed as uF or MFD) 370VAC example.


It is usually strapped to the blower...



I own both of these meters. The Extech is to support my Fluke 902 because my Fluke will not measure millions of Ohms. The Extech is not a heavy duty meter in my opinion.
I have always used Fieldpiece and my next meter will be a Fieldpiece.
 
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Old 04-14-13, 12:17 PM
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Why would the blower start though when switched to "Fan On"? Thanks again for your help.
 
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Old 04-14-13, 12:20 PM
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A weak capacitor struggles to start a motor in the lower heating speeds.
I've seen it a hundred times.

A test would be to measure the heating speed terminals to your blower after the burners ignite and measure the cap.
 
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Old 04-14-13, 12:46 PM
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Sounds like I will be replacing the blower motor capacitor. Thanks and I will let you know what happens...if I don't blow myself up or electrocute myself..
 
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Old 04-14-13, 01:00 PM
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Turn off the power switch or breaker to the furnace and wait a few minutes for the capacitor to bleed down before replacing the capacitor.

The most common size that I see is 10uF x 370VAC but some Lennox blowers use 40uF caps, so be sure to match the specs on your old cap.
 
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Old 04-14-13, 02:46 PM
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I hav the capacitor off..no issues... is there a positive or negative or some other way that the new one has to be attached to the wires? Im off to get a new one at Home Depot..attached is the one that I removed.
 
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Old 04-14-13, 03:10 PM
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The capacitor is non polarized. Just connect one brown wire to each post.
Home Depot does not carry 7.5uF x 370VAC caps in this part of the country.
Grainger or Johnson supply will carry them around here.
 
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Old 04-14-13, 03:52 PM
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Gotta wait until tomorrow....like you said..Home Depot does not carry them. Thanks again for you help and I will update tomorrow after getting the capacitor. Glad the low tonight is only going to be 53 degrees...
 
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Old 04-14-13, 06:11 PM
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Run Capacitor 7.5 MFD 370 Volt - Air Conditioning Replacement Part - Amazon.com

Amazon has them.
Grainger and Johnson are wholesalers and may or may not sell a cap to you.



 
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Old 04-15-13, 10:12 PM
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I got the new capacitor, installed it, hit the breaker and the blower turned on. The thermostat was set to "Fan On" so I switched it off. The temperature was 72 in the house so I waiting until tonight to try the furnace. I put the Thermostat to 72 (temp was 68) and set it to "Auto" and nothing. I tried the "Fan On" and nothing. I check on the furnace, take the doors off and I push in the door switch. I hear a slight hum but nothing happens. Back to square one........
 
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Old 04-16-13, 07:34 PM
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Did we get burner operation but no fan?

If this is the case we need to measure for 120VAC between the heating speed terminal and neutral after flame occurs.

If we are getting voltage to the motor but no fan operation, and the cap is good and correctly wired, we need a motor.
 
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Old 04-17-13, 06:01 AM
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The saga continues. I woke up to 62 degrees inside. The breaker to the furnace was off all night. I put the thermostat on "Fan On" and "Heat". I went downstairs, put the bottom door on the furnance then hit the breaker switch. I then hit the switch for power to the furnace and the blower starts immediately. About 1 minute later, it ignites and we have heat. It has been working for about 45 minutes now. I am afraid that if I switch it from "Fan Only" to "Heat" it will stop again.
 
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Old 04-19-13, 09:31 PM
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A furnace guy came out...it's a bad board... he will replace it monday. Houston thanks for all your help. I appreciate it.
 
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