24VNA6 / 25VNA4: Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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Remove PEV connector from PCM and measure continuity between
pins 1 & 3. If open, inspect wire for damage and repair if necessary. If no
damage is found, replace coil and harness.
Code 64-41 EXV-H Phase Open Lockout
Applies to HP only. EXV-H is required to control superheat in heating
mode. Each time power is applied to outdoor unit the EXV-H will
operate to a known position as the valve does not have the capability to
feedback actual position. The PCM software must know the starting
point and then count as EXV stepper motor is pulsed. At the end of each
cycle the valve will close to help maintain pressure differential and
optimize cyclic efficiency. HP units will not operate if this fault is active
because the valve position at time of failure is unknown.
This code occurs when the PCM determines the resistance of the stepper
motor coil circuit is above the maximum value to properly function.
Inspection of the wire harness and plug should be performed, as well as
using multimeter to confirm "open" continuity between pins. If nothing
is found, replace coil and harness assembly.
Code 64-44 EXV-H Power Shorted Lockout
Applies to HP only. EXV-H is required to control superheat in heating
mode. Each time power is applied to the unit, the EXV-H will operate to
a known position as the valve does not have the capability to feedback
actual position. The PCM software must know the starting point and
then count when stepper motor is pulsed. At the end of each cycle the
valve will close to help maintain pressure differential and optimize
cyclic efficiency. HP units will not operate if this fault is active because
the valve position at time of failure is unknown.
This code occurs when the PCM determines the EXV power supply is
drawing excessive current. The most likely cause of this fault is the wire
attached to pin 1 of EXV-H connector being shorted to ground.
Inspection of the wire harness and plug should be performed, as well as
using multimeter to confirm "short to ground" continuity. If nothing is
found, replace coil and harness assembly.
Code 64-45 EXV-H Phase Shorted Lockout
Applies to HP only. EXV-H is required to control superheat in heating
mode. Each time power is applied to the unit, the EXV-H will operate to
a known position as the valve does not have the capability to feedback
actual position. The PCM software must know the starting point and
then count when stepper motor is pulsed. At the end of each cycle the
valve will close to help maintain pressure differential and opt
imize
cyclic efficiency. HP units will not operate if this fault is active because
the valve position at time of failure is unknown.
This code occurs when the PCM determines the EXV power supply is
drawing excessive current. The most likely cause of this fault is one or
more wires attached to pins 2-5 of EXV-H connector being shorted to
ground. Inspection of the wire harness and plug should be performed, as
well as using multimeter to confirm "short to ground" continuity. If
nothing is found, replace coil and harness assembly.
Code 65-41 EXV-VI Phase Open Lockout
Applies to 5T AC and HP only. EXV-VI is required to operate the vapor
injection circuit which is used in high demand situations such as high
ambient cooling or low ambient heating. Once per day the EXV-VI will
test itself by operating to a known position as the valve does not have the
capability to feedback actual position. The PCM software must know the
starting point and then count when stepper motor is pulsed. The valve
will remain closed until additional capacity is needed.
This code occurs when the PCM determines the resistance of the stepper
motor coil circuit is above the maximum value to properly function.
Inspection of the wire harness and plug should be performed, as well as
using multimeter to confirm "open" continuity between pins. If nothing
is found, replace coil and harness assembly.
Code 65-44 EXV-VI Power Shorted Lockout
Applies to 5T AC and HP only. EXV-VI is required to operate the vapor
injection circuit which is used in high demand situations such as high
ambient cooling or low ambient heating. Once per day the EXV-VI will
test itself by operating to a known position as the valve does not have the
capability to feedback actual position. The PCM software must know the
starting point and then count when stepper motor is pulsed. The valve
will remain closed until additional capacity is needed.
This code occurs when the PCM determines the EXV power supply is
drawing excessive current. The most likely cause of this fault is the wire
attached to pin 1 of EXV-H connector being shorted to ground.
Inspection of the wire harness and plug should be performed, as well as
using multimeter to confirm "short to ground" continuity. If nothing is
found, replace coil and harness assembly.
Code 65-45 EXV-VI Phase Shorted Lockout
Applies to 5T AC and HP only. EXV-VI is required to operate the vapor
injection circuit which is used in high demand situations such as high
ambient cooling or low ambient heating. Once per day the EXV-VI will
test itself by operating to a known position as the valve does not have the
capability to feedback actual position. The PCM software must know the
starting point and then count when stepper motor is pulsed. The valve
will remain closed until additional capacity is needed.
This code occurs when the PCM determines the EXV power supply is
drawing excessive current. The most likely cause of this fault is one or
more wires attached to pins 2-5 of EXV-H connector being shorted to
ground. Inspection of the wire harness and plug should be performed, as
well as using multimeter to confirm "short to ground" continuity. If
nothing is found, replace coil and harness assembly.
Code 66-41 VFD Control Relay Open Lockout
The PCM commands the VFD to close a relay in the power circuit
during VFD initialization. If PCM senses the VFD relay coil is open this
code is set. While this code is active the VFD will not be powered and
system is inoperable. 12VDC is fed from Pins 6&7 of the PCM into pins
5&6 at the VFD via communication cable as long as system is ready to
run (other faults that stop system from operation are not active).
To troubleshoot this fault, remove the PCM-VFD harness from the PCM
while leaving the other end connected to the VFD. Check the resistance
between the pins 6 & 7 of the harness connector. The resistance should
be approximately 720 ohms. If the resistance is much higher than 720
ohms, then remove the connector at the other end of the cable from the
VFD. Check the resistance between pin 6 of the PCM connector and pin
5 of the VFD connector, then pin 7 of the PCM connector and pin 6 of
the VFD connector. If either of these shows a resistance higher than just
a few ohms, then the cable is the cause of the problem. If the cable
checks OK, the problem may be with the VFD. Check the resistance
between pins 5 and 6 of the VFD connector. If this resistance is
significantly higher than 720 ohms, then the problem is within the VFD.
Code 66-42 VFD Control Relay Shorted Lockout
The PCM commands the VFD to close a relay in the power circuit
during VFD initialization. If PCM senses the VFD relay coil is shorted
to ground this code is set. While this code is active the VFD will not be
powered and system is inoperable. 12VDC is fed from Pins 6&7 of the
PCM connector into pins 5&6 of the VFD connector via communication
cable as long as system is ready to run (other faults that stop system from
operation are not active). Check to ensure comm harness is not damaged
and shorting to ground or another wire.
To troubleshoot this fault, remove the PCM-VFD harness from the PCM
while leaving the other end connected to the VFD. Check the resistance
between the pins 6 & 7 of the harness connector. The resistance should
be approximately 720 ohms. If the resistance is much lower than 720
ohms, then remove the connector at the other end of the cable from the
VFD. Check the resistance between pins 5 and 6 of the comm cable
connection at VFD. If this resistance is significantly lower than 720
ohms, then the problem is within the VFD.
VFD Related Faults General Info
Occasional VFD faults may occur that are caused by specific external
circumstances. In these cases the VFD will self-recover and continue to
operate normally. Once faults escalate to malfunctions permanent
damage may be present. The service person should use judgement when
replacing components to determine if occasional external conditions are
present or if equipment is damaged and require replacement because
system is not providing expected performance.
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