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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22512
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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My York Diamond 80 is not working. The 4 light blinks indicate

Customer Question

My York Diamond 80 is not working. The 4 light blinks indicate "limit open". In the past we had a problem with it now working and it was the igniter coil which was replaced. Two weeks ago it went off in the middle of the night and flipping the fuse to the furnace started it back up. That quick fix is not working this time. Could it be as simple as fixing the "limit open" or do I do a new control panel? What to do?
Submitted: 7 years ago.
Category: HVAC
Expert:  BillyHvac replied 7 years ago.


Hello, this is an over temperature switch. Most commonly caused by dirty filter, dirty ac coil above furnace, blocked/insufficient ductwork etc.


It usually resets itself when cool, but yours appears to be stuck.


Behind the gas valve is a flat plate. It has 2 wires attached to it. see if you can identify it and let me know

Customer: replied 7 years ago.
Yes, I have located a black plate (says Texas Instruments on it) with a red wire and a white/yellow wire attached. I doubt it's the AC coil as that system is only 6 months old and all the return ducts are clear. Filter is also 1 week old...I change once a month.
Expert:  BillyHvac replied 7 years ago.


I understand. It is always possible to just have a bad switch.


Turn power off, remove that switch and tap the opposite end where a round bimetal disk is ( you wont see it until it is removed).


Reinstall and see if fault is removed. If not , put the 2 wires directly together and see if fault clears. If so replace switch.

Customer: replied 7 years ago.
I will check that...sorry for the delay. I have an 89-yr old neighbor who needs help moving some boxes, I will respond shortly.
Expert:  BillyHvac replied 7 years ago.
I will leave this open for you...

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