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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8067
Experience:  Furnace, A/C and heat pump specialist.
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I have a lennox merit series furnace (12 years old) and the

Customer Question

I have a lennox merit series furnace (12 years old) and the fan will not run in on position or auto, and furnace will not run. It all ran well with AC this past summer. I cleaned the flame sensor yesterday before trying the furnace. Any ideas where to start troubleshooting?
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Will anything at all work right now? AC or anything?And what type thermostat do you have ,digital or mechanical?

Customer: replied 1 year ago.
No. I think it's a mechanical thermostat. I came with the unit and the house 12.5 years ago.
Expert:  airheatman replied 1 year ago.

Troubleshooting often requires meters and test equipment.Do you have a multi meter for testing voltage? If not you can get an inexpensive one at Walmart for about 15 bucks, if you have or would like to obtain a meter to troubleshoot , I will be happy to guide you.Without a meter , there are a limited number of things we can check if you are able to do a visual inspection and can do some hands on troubleshooting.Please let me know and we can go from here.

Customer: replied 1 year ago.
I do have a harbor freight tester. And I would be willing to try any types of testing or inspecting
Expert:  airheatman replied 1 year ago.

Your furnace has a control board located in the blower compartment that will help us in troubleshooting. Look and see if there is a little window to look through on bottom panel and see what light is doing. Here is a chart.I will guide you from here.

Customer: replied 1 year ago.
No light in window, I checked already
Customer: replied 1 year ago.
Are you still there. There is no light red or green?
Expert:  airheatman replied 1 year ago.

OK if no light is on at all we are not getting power to the furnace control board. Lets remove that panel and check power coming in.

Customer: replied 1 year ago.
OK, panel is removed
Expert:  airheatman replied 1 year ago.

Are you fAMILIAR WITH A TRANSFORMER , WHAT IT LOOKS LIKE?

Customer: replied 1 year ago.
Not real sure, but I'm willing to learn:)
Expert:  airheatman replied 1 year ago.

OH here is the transformer. It will have 2 wires coming in to LINE and two wires leaving from LOAD.

We want to verify 120v into line and 24v out of load

http://www.repairclinic.com/PartDetail/b367p36/Lennox-Furnace-Transformer/17W56/2345689?modelNumber=G40UH-36A-070-5&ss=a36b367d1238076&mr=1

Expert:  airheatman replied 1 year ago.

Keep in mind door switch will need to be held ot taped in to get power to furnace

Customer: replied 1 year ago.
Going to try phone, it's easier than running up and down the stairs.
Customer: replied 1 year ago.
Expert:  airheatman replied 1 year ago.

Thanks for letting me work wit you.Feel free to follow up for 30 days at no additional cost. Bonus always appreciated if you feel justified

Customer: replied 1 year ago.
Fuse blown. Thanks for the help!!! A+++++
Expert:  airheatman replied 1 year ago.

If my answer has been polite, professional,and thorough, please click one of the ratings before you go. If you still need help let me know!.Expert is not paid for assisting you until you rate answer