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Table 23 — Diagnostic Codes
NOTES:
1. Illegal unit configuration caused by missing programmable header or both unloader DIP switches on.
2. All auto. reset failures that cause the unit to stop will restart when the error has been corrected.
3. All manual reset errors must be reset by turning the control switch off and then back on.
4. Valid resistance range for the thermistors is 363,000 to 585 ohms.
5. Codes 53, 54, 57, 58, 61, 62, 65-69, 73, 74, and 77-80 are not used on these units.
CODES 59 AND 60: LOW-PRESSURE SWITCH — These
codes are used to indicate a low-pressure switch failure.
The processor monitors the low-pressure switch. If the
switch opens, either by low refrigerant charge, circuit failure,
or wiring error, the circuit is locked off. Code 59 indicates a
failure of the lead circuit, and as a result, that circuit will be
shut down. Code 60 indicates a failure of the lag circuit, and as
a result, that circuit will be shut down. These codes will only be
displayed when the display button is pressed. To reset the cir-
cuit, the ON-OFF switch must be turned to OFF, then ON
position.
CODES 63 AND 64: OIL PRESSURE SWITCH — These
codes are used to indicate an oil pressure switch failure. Since
the units do not have oil pressure switches, these codes are not
used. The terminals on the processor board must be jumpered
together or an error will occur. If these errors occur, check
jumper between J2-1 and J2-2 for a code 63, or between J2-3
and J2-4 for a code 64 to be sure jumper is properly connected.
To reset the circuit, the ON-OFF switch must be turned to OFF
and then to ON position.
CODE 70: ILLEGAL UNIT CONFIGURATION — If the
unit configuration header is not installed and properly config-
ured, and/or if DIP switches are not properly set, unit will not
start, and an error code of 70 will be indicated on display board
when display button is pushed. Check the header and DIP
switch settings.
CODES 71 TO 76: THERMISTOR/RESISTOR FAILURE —
If measured temperature of a thermistor is less than –60 F
(363,000 ohms) or greater than 180 F (585 ohms), the appro-
priate sensor error code (Table 23) will be displayed when
the display button is pushed. The unit will be shut down.
Thermistor failures will automatically reset once the error has
been corrected. If a failure occurs, the following are possible
causes:
Thermistor or Resistor Failure
— A shorted or open ther-
mistor or resistor will cause the failure.
Wiring Failure
— If a wiring error exists that causes a shorted
or open circuit, this will cause a failure.
Processor Board Failure
— If circuitry on processor board
fails, this could cause an error.
The codes are designated as follows:
Code 71 Supply-Air Thermistor Failure
Code 72 Return-Air Thermistor Failure
Code 73 Not used
Code 74 Not used
Code 75 Circuit 1 Saturated Condensing Thermistor
Code 76 Circuit 2 Saturated Condensing Thermistor
CODE 81: RESET THERMISTOR OR POTENTIOMETER
FAILURE — This is a unique code since the reset temperature
potentiometer (P7) is in series with the space temperature ther-
mistor (T10). If either one of these components fail, reset will
be terminated. This error will automatically reset once the situ-
ation is corrected. If an error is detected, the most probable
cause is one of the following:
• Thermistor Failure — A shorted or open thermistor will
cause the failure.
• Potentiometer Failure — If the potentiometer is outside
of the valid range (40 to 90 F), a failure will result.
• Wiring Problem — If the circuit is open, a failure will be
detected.
• Processor Board Failure — If the processor board fails
(hardware), an alarm will be detected.
DISPLAY DESCRIPTION OF FAILURE
ACTION TAKEN
BY CONTROL
RESET
METHOD
PROBABLE CAUSE
51
55
52
56
Compressor 1 failure
Compressor 2 failure
Compressor 3 failure
Compressor 4 failure
Circuit 1 shut off
Circuit 2 shut off
Compressor 3 shut off
Compressor 4 shut off
Manual
Manual
Manual
Manual
High-pressure switch or high dis-
charge gas thermostat switch
trip, compressor ground current
>2.5 amp or compressor board
relay on when it is not supposed
to be on. Wiring error between
electronic control and compres-
sor protection module.
59
60
Loss-of-charge circuit 1
Loss-of-charge circuit 2
Circuit 1 shut off
Circuit 2 shut off
Manual
Manual
This indicates either a low refrig-
erant charge, or a loss-of-charge
switch failure.
63
64
Low oil pressure circuit 1
Low oil pressure circuit 2
Circuit 1 shut off
Circuit 2 shut off
Manual
Manual
Not used; Check jumper on pro-
cessor board.
70
Illegal unit configuration Unit will not start Manual Configuration error (see Note 1).
71
72
75
76
81
Supply-air thermistor failure
Return-air thermistor failure
Circuit 1 saturated condensing thermistor
Circuit 2 saturated condensing thermistor
Reset temperature thermistor failure
Unit shut off
Use default value
Unit shut off
Unit shut off
Stop reset
Auto.
Auto.
Auto.
Auto.
Auto.
Thermistor or resistor failure, wir-
ing error, or thermistor or resistor
not connected to the processor
board.
82
83
84
85
86
87
Supply-air set point potentiometer failure
Economizer potentiometer failure
Reset limit set point potentiometer failure
Demand limit potentiometer failure
Minimum economizer potentiometer failure
Warm-up set point potentiometer failure
Use default value
Close economizer
Stop reset
Stop demand limit
Close economizer
Use default value
Auto.
Auto.
Auto.
Auto.
Auto.
Auto.
Potentiometer improperly con-
nected, potentiometer setting out
of range, potentiometer failure or
wiring error.