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BillyHvac
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22245
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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8 Year Old Lenox AC Unit: Furnace: Model # *****

Customer Question

8 Year Old Lenox AC Unit:
Furnace: Model # ***** Serial # *****
Coil: Model # ***** Serial# *****
Thermostat: Honeywell Vision Pro Th8000 Series TH8110U
Problem:
In Cooling Mode the AC Unit sometimes shuts down for no apparent reason. To restart the system, through trial and error, I have found that if I switch the furnace power off/on and turn the thermostat off/on, the AC Unit will restart in the cooling mode and run without a problem. This problem has occurred sporadically 1 to 4 times during a cooling season. Is there any way to diagnosis what is causing the problem – control board, thermostat, etc…? I have a smaller upstairs AC Unit that has run for 8 years without a problem.
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.
hello, this is a very tough issue to diagnose....is there a water drain safety switch incorporated into a condensate pump? Use reply
Customer: replied 1 year ago.
Billy, thanks for connecting. There is no drain safety switch. Unit is in attic. Condensate just drains from pan via gravity to grade.
Expert:  BillyHvac replied 1 year ago.
If the unit is in attic...by code it is supposed to have a at minimum a drain safety pan switch. Is there a sign of any water?
Customer: replied 1 year ago.
No water build up in pan. Not sure that Texas State code requires a safety switch. My home is 8 years old.
Expert:  BillyHvac replied 1 year ago.
any unit in an attic...in every state requires a drain or pan safety to protect ceiling and structure in event of plugged drain. These can make stop and starts common with no idea of where breach is. When this happens does the diagnostic light on furnace circuit board flash a code?
Customer: replied 1 year ago.
Unit has drain pan. Never any condensate buildup. Condensate drains freely to grade through plastic tube via gravity. Never any flashing code.
Expert:  BillyHvac replied 1 year ago.
ok....well given that it comes back on with a reset rules out bad wiring...you say there is NO water drain, pump or drain safety..
This leaves thermostat or circuit board...
Customer: replied 1 year ago.
What do you recommend?
Expert:  BillyHvac replied 1 year ago.
I would have to say board as a thermostat glitch would not reset in the manner a board would....which is what yours is doing.
Customer: replied 1 year ago.
I believe the board is warranted for 10 years and the unit is only 8 years old. As the unit is now running properly in the cooling mode, and the "failure" event only happens 1 to 4 times during the cooling system, how do I convince manufactuer to provide new board for free?
If I wait to next "failure" event and do not not get the unit running myself and instead call an authorized Lennox service provider, would service person be able to confirm through diagnostic testing that the board is defective?
Expert:  BillyHvac replied 1 year ago.
I understand what you are asking....but unfortunately , without conducting test on site, I do not have enough data to answer this.
When we have irregular breakdowns like this we install a data logger and tattletails.
This way when it breaks down we have confirmation of volts, amps, pressure and temperature and the issue that caused failure. Without data loggers it is very hard to confirm.
All I could recommend is if it breaks down again...leave it totally alone, do not reset and call for service.