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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Code 88-34 VFD Internal Fault - PFCM Sensor A
Code 88-74 VFD Lockout - PFCM Sensor A
The VFD has internal current measurement to protect PFC components
from exceeding current thresholds that may shorten the VFDs operating
life. If the PFCM Sensor A exceeds safe reliable value, the VFD will
shut down immediately and attempt a restart after 5 minute compressor
protection timer expires. Three occurrences of code 88-34 within a 4
hour period will result in 88-74 malfunction and 4 hour lockout. While
this fault or malfunction is active the unit is inoperable. This
malfunction, once set, is unlikely to go away and indicates VFD damage.
Manually power cycle outdoor unit with disconnect, if malfunction
persists replace VFD.
Code 88-35 VFD Internal Fault - PFCM Sensor B
Code 88-75 VFD Lockout - PFCM Sensor B
The VFD has internal current measurement to protect PFC components
from exceeding current thresholds that may shorten the VFDs operating
life. If the PFCM Sensor B exceeds safe reliable value, the VFD will
shut down immediately and attempt a restart after 5 minute compressor
protection timer expires. Three occurrences of code 88-35 within a 4
hour period will result in 88-75 malfunction and 4 hour lockout. While
this fault or malfunction is active the unit is inoperable. This
malfunction, once set, is unlikely to go away and indicates VFD damage.
Manually power cycle outdoor unit with disconnect, if malfunction
persists replace VFD.
Code 88-36 VFD Internal Fault - Line Volt Sens
Code 88-76 VFD Lockout - Line Volt Sensor
The VFD has internal voltage measurement to protect components from
operating outside of voltage thresholds that may shorten the VFDs
operating life. If the line volt sensor value is outside of safe reliable
range, the VFD will shut down immediately and attempt a restart after 5
minute compressor protection timer expires. Three occurrences of code
88-36 within a 4 hour period will result in 88-76 malfunction and 4 hour
lockout. While this fault or malfunction is active the unit is inoperable.
This malfunction, once set, is unlikely to go away and indicates VFD
damage. Manually power cycle outdoor unit with disconnect, if
malfunction persists replace VFD.
Code 88-37 VFD Internal Fault - PFCM Temp Sens
The VFD has internal temperature sensors to monitor critical power
components and take action if operating temperatures cross thresholds
that may shorten the VFDs operating life. If the PFCM temperature
sensor fails it will no longer be capable of preventing the PFC circuit
from operation above the safe reliable temperature threshold. If this fault
is active the VFD will continue to operate normally, since the only way
to correct this fault is to replace VFD.
Code 88-38 VFD Internal Fault - DC Discharge
Code 88-78 VFD Lockout - Int DC Discharge
The unit VFD converts boosts 230VAC line voltage and then converts to
DC voltage before switching the DC voltage on and off rapidly to create
a 3 phase waveform and operate compressor at varying speeds. This
fault becomes active when the DC voltage is shorted to ground and the
VFD will open the power relay. While this fault or malfunction is active
the unit is inoperable. The VFD will attempt to reset itself automatically
but if problem persists, the fault will escalate to 88-78 malfunction and
lock out system for 4 hours. Manually power cycle outdoor unit with
disconnect, if malfunction persists replace VFD.
Code 88-39 VFD Internal Fault - Microprocessor
Code 88-79 VFD Internal Lockout - Microprocessor
This VFD has internal diagnostics to verify that the microprocessor is
operating sufficiently to maintain safe compressor and fan operation. If
the microprocessor detects any abnormal condition that could result in
unsafe operation it will set a diagnostic code. If this occurs, the PCM
will set 88-39 and reset the VFD to attempt to remedy the condition. If
this attempt is unsuccessful, malfunction Code 88-79 will be set and the
system will be locked out for 4 hours. Manually power cycle the
outdoor system. If the diagnostic code persists replace the VFD.