When the thermostat light [Emergency Heat Light] is flashing or on during normal operation, this indicates the outdoor unit is "locked-out".
This means the outdoor unit has shut itself down because of a problem and it sends a signal to the thermostat, letting you know there is a problem. When this happens, the indoor unit tends to keep on running because the indoor unit doesn't know there is a problem. And if the outdoor unit isn't running, the indoor unit will most likely never satisfy the thermostat.
Many systems, like the York Stellar Series units have a diagnostic feature. When you see the light flashing, it flashes a code. You can count the number of flashes, usually between two and nine and then it just repeats itself. You can now reset the system by turning the thermostat "off", waiting thirty seconds then back "on" again. This should restart the system but may take up to 10 minutes.
Some systems require shutting the power to the indoor unit off momentarily, then back on. The light should also go out. After 10 minutes, see if the outdoor unit is running. If the light doesn't go out or if the unit doesn't start, you may need to call for service assuming you checked for the obvious, like tripped breakers or the outdoor reset button.
Sometimes a unit will "lock-out" on a fluke or a weather-related condition and resetting will solve the problem. But if the unit "locks-out" again, most likely there is a problem and service will be needed.
Below is a list of possible causes. Items in blue usually require a service call. Items in red however can be addressed, even fixed by the homeowner.
York Stellar Flash Code:
Module:
2 code- off on high pressure
3 code- off on high discharge temperature
4 code- off on low discharge temperature
5 code- default defrost, defrosting too often
7 code- bad ambient sensor
8 code- bad liquid-line sensor
Other systems:
High pressure or high temperature switch opened
Low pressure or low temperature switch opened
Defrosting too much
High pressure switch opened - some units have manual reset button outside - possible cause: blocked air filter or coil, bad fan motor, overcharge, running heat on a hot day, stuck contactor in heating mode
The bottom causes in red are common problems and can be addressed by the homeowner. Try to check for these conditions first before calling for service.
Hope this helps, remember - these are just rough guidelines and not all possible situations are covered.
Hannabery HVAC is registered with the Commonwealth of Pennsylvania's Office of Attorney General: PA#8215
