Heat Controller VMH09SC-1 Service Manual page 41

Heat Controller, Inc.
9.29 P3 ERROR – Low Ambient Protection
If the outdoor temperature remains at 5°F(-15°C) for an hour, the compressor will turn off and the error
code "P3" will be displayed on the indoor unit. Once the compressor has been off for at least an hour and
the temperature outside is equal to or greater than 10.4°F(-12°C) for at least ten minutes, the system will
restart. Additionally if the outside temperature reaches at least 41°F(5°C) for at least ten minutes, the
system will restart without the needed 1 hour compressor off time required.
P4:
9.2.10 Inverter compressor drive error diagnosis and solution
Is the connection of compressor good?
Is the wiring sequence right? The voltage
range proper?
Yes
Replace the outdoor PCB
9.2.9 Zero crossing check resistance or inverter compressor, it is .7Ω error
Alarm signal when the main chip can't detect over-zero signal. When such failure occurs, the main control
board must have fault.
Check power supply and
connections
Indoor PCB defective
VMH SerieS
No
Reconnect and retry
No
Replace inverter compressor.
Correct power supply or
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correct connections
Service Manual