Mitsubishi Fault codes

[steptoe111]

Hi guys,First post in quite awhile.
Have an issue with a Mitsubishi MR SLIM A/C,MODEL PUH-5YKSA (Australia). Hope one of the experts can help me with the fault codes, specifically the P8 fault. Cheers steptoe111

[nike123]

Indoor unit pipe probe temperature abnormal.

Look what simple search function of this forum returns when you search for "fault codes"

http://www.refrigeration-engineer.com/forums/search.php?searchid=633108

[steptoe111]

Many thanks Nike,not finding this site very easy to navigate yet! I read from your reply that the system is suffering from low refrigerant syndrome? Cheers

[nike123]

Many thanks Nike,not finding this site very easy to navigate yet! I read from your reply that the system is suffering from low refrigerant syndrome? Cheers
If the termistor is OK, then possibility is that is refrigerant amount, or air flow problem!

[Thermatech]

On the old R22 Mr Slim units the indoor unit could only send 2 commands to the outdoor unit using 12v d/c 3 core interconnecting cable.
1/ compressor on
2/ Reversing valve energized.


The outdoor unit was unable to send any data back to the indoor unit.

The way the indoor unit detected any problem with the outdoor unit was by constantly monitoring the refrigerant temperature at the indoor coil & difference from room return air.

In cooling the indoor unit reports P8 if the difference between return air & refrigerant coil temp is less than 5 deg C for about 8 mins.
The coil temp must be more than 5 deg C below room return air temp for the indoor unit to consider that the outdoor unit is operating.

So P8 covers a multitude of sins.
possibilities are
1/ indoor unit temperature sensors reading incorrect temperature.
2/ Some sort of problem with the outdoor unit.
3/ incorrect interconnecting wiring connections.
4/ interconnect cable from indoor unit connected to another outdoor unit (crossed pipes & control cable between multiple systems)

A good place to start is at the outdoor unit circuit board.
There is a row of red LED's on the control circuit board.
If any are blinking then look at the label on the service access panel which should have a list of the faults indicated by the blinking LED's.

[martin102]

On the old R22 Mr Slim units the indoor unit could only send 2 commands to the outdoor unit using 12v d/c 3 core interconnecting cable.
1/ compressor on
2/ Reversing valve energized.


The outdoor unit was unable to send any data back to the indoor unit.

The way the indoor unit detected any problem with the outdoor unit was by constantly monitoring the refrigerant temperature at the indoor coil & difference from room return air.

In cooling the indoor unit reports P8 if the difference between return air & refrigerant coil temp is less than 5 deg C for about 8 mins.
The coil temp must be more than 5 deg C below room return air temp for the indoor unit to consider that the outdoor unit is operating.

So P8 covers a multitude of sins.
possibilities are
1/ indoor unit temperature sensors reading incorrect temperature.
2/ Some sort of problem with the outdoor unit.
3/ incorrect interconnecting wiring connections.
4/ interconnect cable from indoor unit connected to another outdoor unit (crossed pipes & control cable between multiple systems)

A good place to start is at the outdoor unit circuit board.
There is a row of red LED's on the control circuit board.
If any are blinking then look at the label on the service access panel which should have a list of the faults indicated by the blinking LED's.

What would you do if there were no leds lit on outdoor pcb?

[hyperion]

Fistly check for mains power at condensing unit. If that is correct and turning the power off for a couple of minutes and then re-instating power then pressing SW2 button should change over the display mode. LD8 should be lit to indicate that power is on for the crankcase heater. Post back for next set of info.