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24 VAC Power Wiring
The diagnostic module requires a constant nominal 24 VAC
power supply. The wiring to the module’s R and C terminals must
be directly from the indoor unit or thermostat. The module cannot
be powered by R and C terminals on the defrost board without
experiencing nuisance alerts.
Thermostat Demand Wiring
The diagnostic module requires a thermostat demand signal to
operate properly. The thermostat demand signal input, labeled Y
on the module, should always be connected to the compressor
contactor coil so that when the coil is energized, the demand
signal input is 24 VAC. When the coil is not energized, the
demand signal input should be less than 0.5 VAC.
Alert (Yellow) Flash Code 3 Short Cycling: Compressor is
running only briefly.
■ Thermostat demand signal is intermittent.
■ Time delay relay or control board is defective.
■ If high pressure switch is present, go to Flash Code
2 information.
■ If low pressure switch is present, go to Flash Code
1 information.
Alert (Yellow) Flash Code 4 Locked Rotor
■ Run capacitor has failed.
■ Low line voltage (contact utility if voltage at disconnect is low).
■ Excessive liquid refrigerant in the compressor.
■ Compressor bearings are seized.
Alert (Yellow) Flash Code 5 Open circuit
■ Outdoor unit power disconnect is open.
■ Compressor circuit breaker or fuse(s) is open.
■ Compressor contactor has failed to open.
■ High pressure switch is open and requires manual reset.
■ Open circuit in the compressor supply wiring or connections.
■ Unusually long compressor protector reset time due to the
extreme ambient temperature.
■ Compressor windings are damaged.
Alert (Yellow) Flash Code 6 Open Start Circuit: Current
only in run circuit.
■ Run capacitor has failed.
■ Open circuit in the compressor start wiring or connections.
■ Compressor start winding is damaged.
Alert (Yellow) Flash Code 7
NOTE: This code will
flash within 5 minutes of
power interruption until the
5 minute short cycle timer
has elapsed. Allow at least
5 minutes of run time before
confirming this code.
Open Run Circuit: Current
only in start circuit
■ Open circuit in the compressor run wiring or connections.
■ Compressor run winding is damaged.
Alert (Yellow) Flash Code 8 Welded Contactor:
Compressor always runs.
■ Compressor contactor has failed to close.
■ Thermostat demand signal not connected to the module.
Alert (Yellow) Flash Code 9 Low Voltage: Control circuit
less than 17 VAC
■ Control circuit transformer is overloaded.
■ Low line voltage (contact utility if voltage at disconnect is low).
Flash Codes
LED Status Fault Description Troubleshooting Information