24VNA6 / 25VNA4: Service Manual
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Code 53-42 OST Shorted - Backup Heat Only
The suction thermistor is required for control of the outdoor EXV in HP
systems. Similar to "OST Open" fault, heating mode operation will be
locked out if the OST is determined to be open or shorted. Cooling
operation will be allowed if OST is not functional, though on HP
systems the malfunction will be displayed on wall control screen. This
will remind homeowner to repair the sensor before heating season.
Shorted OST sensor value will default to "47" on status or checkout
display. The sensor is monitored continuously and if resistance is below
1kohm for 1 second this fault will occur. Once sensor value rises above
1kohm for 1 second the fault will clear.
Measure resistance value of thermistor at the PCM connector. If value is
below 1kohm, look for bare wire, short in the wiring, or at the connector
itself. If no bare wires or shorts are observed, replace sensor. If measured
resistance is within allowable range, replace PCM.
Code 54-01 ODT Open
The discharge thermistor is used to protect the compressor and ensure
discharge superheat is present at all times. When "ODT Open"
malfunction is active 47 will be substituted by default. The sensor is
monitored continuously and if resistance is above 310kohm for 1 second
this malfunction will occur. Once sensor value drops below 310kohm for
1 second the malfunction will clear. Since achieving discharge superheat
is an integral requirement for startup, when this sensor does not read a
valid value, the system will only run at startup speed. Normal operation
will resume once valid ODT value is read by PCM.
Measure resistance value of thermistor at the PCM connector. If value is
above 310kohm, and OAT and OCT measure above 25F, look for a break
in the wiring or at the connector itself. If no breaks are observed, replace
sensor. If measured resistance is within allowable range, replace PCM.
Code 54-02 ODT Shorted
The discharge thermistor is used to protect the compressor and ensure
discharge superheat is present at all times. When "ODT Shorted"
malfunction is active 47 will be substituted by default. The sensor is
monitored continuously and if resistance is below 670 ohm for 1 second
this malfunction will occur. Once sensor value rises above 670 ohm for 1
second the malfunction will clear. Since achieving discharge superheat is
an integral requirement for startup, when this sensor does not read a
valid value, the system will only run at startup speed. Normal
operation
will resume once valid ODT value is read by PCM.
Measure resistance value of thermistor at the PCM connector. If value is
below 670 ohm, look for a short in the wiring or at the connector itself. If
no shorts are observed, replace sensor. If measured resistance is within
allowable range, replace PCM.
Code 57-01 P1 Open Fault
Code 57-41 P1 Open Lockout
Code 58-01 P2 Open Fault
Code 58-41 P2 Open Lockout
Pressure transducers are dynamically assigned based on their relative
values within PCM software. This feature allows the pressure
transducers and harnesses to be interchangeable. Each pressure
transducer requires 3 wires: Ground (BLK), Power (+5V DC, RED), and
Signal (GRN). The ratio of voltage between power and signal wires is
converted into a pressure value. If the signal is above or below the
pressure transducers ability to measure it may be because the power wire
is not supplying 5V DC or the signal wire is not returning a DC Voltage
between 0.5-4.5 VDC. A base code of 57 or 58 is determined based on
which PCM connection has the issue, P1 or P2. The expansion codes 01
and 41 explain the type of issue, in this case "open", meaning the signal
wire is returning more than 4.5V DC. The most likely cause of this the
sensor wire being disconnected and the PCM board "pulling" up the
signal voltage to +5V DC.
Code 57-02 P1 Shorted Fault
Code 57-42 P1 Shorted Lockout
Code 58-02 P2 Shorted Fault
Code 58-42 P2 Shorted Lockout
Pressure transducers are dynamically assigned based on their relative
values within PCM software. This feature allows the pressure
transducers and harnesses to be interchangeable. Each pressure
transducer requires 3 wires: Ground (BLK), Power (+5V DC, RED), and
Signal (GRN). The ratio of voltage between power and signal wires is
converted into a pressure value. If the signal is above or below the
pressure transducers ability to measure it may be because the power wire
is not supplying 5V DC or the signal wire is not returning a DC Voltage
between 0.5-4.5 VDC. A base code of 57 or 58 is determined based on
which PCM connection has the issue, P1 or P2. The expansion codes 02
and 42 explain the type of issue, in this case "shorted", meaning the
signal wire is returning less than 0.5V DC. The most likely cause of this
the sensor wire being shorted to the metal chassis.
Code 57-43 P1 Sensor Lockout
Code 58-43 P2 Sensor Lockout
Pressure transducers are dynamically assigned based on their relative
values within PCM software. For this reason the pressure transducers
and harnesses are interchangeable. Each pressure transducer requires 3
wires: Ground (BLK), Power (+5V DC, RED), and Signal (GRN). The
ratio of voltage between power and signal wires is converted into a
pressure value. The pressure transducer is capable of sending a
value to
PCM via sensor wire if it is not working correctly. A base code of 57 or
58 is determined based on which PCM connection has the issue, P1 or
P2. When a DC V value of 4.84-4.95 is returned to PCM it will trigger
57-43 or 58-43 fault. The most likely cause of this is a failed transducer
part. Switch the harnesses from P1 and P2 to see if the malfunction
follows the transducer. If so, follow procedure to replace failed pressure
transducer. Trace wires from PCM board connection to ensure correct
transducer is being replaced.
Code 61-13 Reversing Valve Timeout Fault
Code 61-53 Reversing Valve Timeout Lockout
Applies to HP only. The reversing valve is required to be energized for
cooling operation and for defrosting during heating operation. The
reversing valve will only actuate when the pressure difference between
the suction and discharge of the compressor is above a minimum level.
The 61-13 will be set whenever the minimum pressure condition
prevents a reversing valve switch for 10 minutes. The 61-53 will be set
when the 61-13 has been set 4 times in 2 hours. The 61-53 will result in a
2 hour lockout. When this fault occurs it may be due to the reversing
valve being stuck between the heating and cooling positions, or the
compressor is not pumping properly. If this lockout occurs repeatedly
then a reversing valve or compressor replacement may be needed.
Code 61-41 RVS Open Lockout
Applies to HP only. Reversing valve is required to be energized for
cooling operation, and for defrosting during heating operation, therefore
the system will declare 61-41 when it senses the reversing valve coil is
"open" or infinite resistance, and not operational. This check can only be
performed when the reversing valve is not energized so it is possible that
a reversing valve coil failure during the cooling season may not be
identified since the reversing valve continues to be powered between
cooling cycles. In this case the system will not declare a fault but the
reversing valve will be in the heating position.
Remove RVS connector from PCM and measure continuity between
pins 1 & 3. If open or shorted, inspect wire for damage and repair if
necessary. If no damage is found, replace coil and harness.
Code 62-01 PEV Solenoid Open
PEV (pressure equalization valve) is used to equalize pressures across
the compressor prior to starting in order to ensure the compressor can
align itself and start will minimal effort. The system will declare 62-01
when it senses the PEV coil is "open" or infinite resistance. The system
will continue to operate while this fault is active as long as
the pressures
are within acceptable range prior to start attempt. If not, the system will
not start until pressure differential drops to acceptable range.
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