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Thermostat Flashing

Thermostat Flashing

THERMOSTAT FLASHING – Some York heat pumps and air conditioners utilize a computerized equipment monitoring system which will flash a “diagnostic” light at the thermostat to indicate a problem or system malfunction. Most alarms and alerts require a qualified service technician to diagnose. However, there are some problem you may be able to resolve yourself.

*All diagnostics will attempt to reset by turning the thermostat "Off" for several minutes, then back to "Heat" or "Auto". Be sure to count the diagnostic flashes before resetting from the thermostat.


No Power to the Outdoor Unit

If there is no power to the outdoor unit for an extended period, the YorkGuard will flash a code 4 - Low Discharge Temperature.

Check the breaker for the heat pump and make sure that it is not tripped. Watch Video. If the breaker is okay, a qualified service technician should check the system.

Dirty/Clogged Air Filter or Indoor Coil

A dirty or clogged air filter will reduce airflow across the indoor coil which can cause a high pressure condition.

A clogged air filter will generally be identified by a weak flow of air from the registers.

If these symptoms are identified, try removing or changing the filter to see if the conditions improve.

In the heating mode, a clogged filter, dirty indoor coil or restricted ductwork can cause a code 2 - High Pressure Fault.

Refrigerant Issues - Qualified Technician Recommended

If a heat pump equipped with a YorkGuard module experiences a refrigerant issue that effects equipment operation, it will shut-off and display a "Code 2,3,4 or 5" at the thermostat.

Low refrigerant charge (usually the result of a refrigerant leak) can cause the compressor to overheat. An overheat condition may cause a code 3 - High Discharge Temperature.

In the heating mode, low charge can also cause the outdoor coil to freeze prematurely and may cause a code 5 - Default Defrost.

A unit with excesses refrigerant charge may experience a high-pressure situation which may cause a code 2 - High Pressure Fault.

Excess charge can also over-cool the compressor and cause a code 4 - Low Discharge Temperature.

Defrost Problem - Qualified Technician Recommended

If the YorkGuard sees a problem in the defrost sequence, it will display a "Code 5" at the thermostat.

Issues that may cause a code 5 are low refrigerant, bad outdoor fan motor or capacitor (below), stuck reversing valve, or bad defrost sensor.

If the outdoor unit is severely frozen you should turn the thermostat to emergency heat and contact a qualified technician to diagnose.

DO NOT attempt to chip ice away from the outdoor coil.

Bad Blower Motor - Qualified Technician Recommended

If the blower motor does not operate during a heating cycle, high refrigerant pressure will occur.

A non-operating blower motor in the heating mode will cause a code 2 - High Pressure fault.

If the blower motor hums but does not start, it is most likely a bad motor or a bad capacitor (below).

A bad blower motor is often accompanied by a bad smell like burning rubber or plastic.

Bad Outdoor Fan Motor - Qualified Technician Recommended

The outdoor fan motor should run any time the compressor is operating in the heating mode except during a defrost cycle.

If the compressor starts but the fan does not, either the motor or its starting capacitor (below) is likely bad.

A bad outdoor fan motor in the heating mode will typically cause a code 5 - Default Defrost.

Bad Capacitor - Qualified Technician Recommended

Most direct-drive PSC fan motors require a capacitor which provides extra power for starting.

A fan motor with a bad capacitor will typically attempt to start but will fail while making a louder-than-normal humming noise.

After several seconds of humming, the motor will typically overheat and shut-off and then retry after about 30-60 seconds of cooling.

A fan motor that runs normally after helping to start by turning by hand usually indicates a bad capacitor.

Bad Compressor - Qualified Technician Recommended

The compressor in a heat pump pumps the refrigerant and provides the compression for heating and cooling to take place.

A compressor can have several malfunction conditions, each of which can cause a code 4 - Low Discharge Temperature.

A "shorted" compressor will usually cause the breaker to trip every time it tries to start.

A "locked-up" compressor will typically fail to start. It will often making a brief growling noise and may pull enough amperage to trip the breaker (a bad start capacitor can cause the same symptoms).

A compressor with "bad valves" will generally start normally but will either produce very little or no compression.

Bad Sensor - Qualified Technician Recommended

There are three sensors on a YorkGuard module - Outdoor Temperature, Liquid Line Temperature and Compressor Discharge Temperature.

If the YorkGuard detects a bad sensor, it will display a "Code 6, 7 or 8" at the thermostat.

Our focus and specialty is quality installation, service and repair of heating and air conditioning systems - both residential and commercial.

For more than 45 years, GHAC, Inc. has been the trusted name in HVAC for customers all across the Tri-State.

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