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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8369
Experience:  Furnace, A/C and heat pump specialist.
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I have a Honeywell wireless programmable thermostat and a

Customer Question

I have a Honeywell wireless programmable thermostat and a Lennox Merit gas furnace. The heat turns off at the desired temp but 75% of the time it will not turn back on. Right now it is set at 70 degrees (auto) and the room temp is 65. If I go to the furnace and turn the power off and back on it will turn on and heat to the target temp but again, once it shuts off it frequently will not come back on. If I detach the Honeywell thermostat and then immediately reattach it, the system will also turn on. I cleaned the flame sensor and checked the condensation line for backup but it didn't solve the problem. I should mention that this has just started happening since the outside temp dropped from the 30s to the teens. Coincidence? Do I have a bad thermostat or is it something with the furnace?
Submitted: 9 months ago.
Category: HVAC
Customer: replied 9 months ago.
I also confirmed that the thermostat was level
Expert:  airheatman replied 9 months ago.

Lets start by determining if issue is with thermostat or furnace.

Can you give me complete model from inside furnace in burner compartment so I can provide guidance with this specific unit.Model will be on a label just above burners on right or left inside panel

Then look in blower compartment and see if we have a control board with a blinking light.If so tell me the pattern of that flash when it should be on but is not .That will indicate what is wrong and tell us where to start troubleshooting.

Customer: replied 9 months ago.
The model number is ***** When I opened the panel (the unit was not running) there were two slowly flashing green lights labeled DS1 and DS2 on the SureLight panel which then went out. I depressed the plunger as if the panel was closed and they started flashing quickly and the furnace started up.
Expert:  airheatman replied 9 months ago.

OK we need to see what the lights do when it fails. If there is not a window to look in, you will need to hold or tape door switch in to see because when you remove panel door switch pops out and kills power to furnace.

Customer: replied 9 months ago.
Ok. It has a small window I didn't notice before. Will check when able
Expert:  airheatman replied 9 months ago.

Let m know and we will go from there

Customer: replied 9 months ago.
It should be on now and isn't. The green lights are alternating flashing back and forth.
Expert:  airheatman replied 9 months ago.
Customer: replied 9 months ago.
Interesting. It's a fast alternating flash but I tested the voltage and I'm getting 110. Not sure how to check for an improper main ground and it's been installed for years with no problem. It comes on just fine if cycled off and on at the switch.
Expert:  airheatman replied 9 months ago.

If power is good and ground is secure you probably have a board going bad.

Customer: replied 9 months ago.
Sounds like that's probably the case.
Expert:  airheatman replied 9 months ago.

MIght want to have an onsite verify there is nothing simple that I cant see by internet though.

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

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