Indoor unit and outdoor unit not connecting - NG Weather NATIONAL GEOGRAPHIC 265NC

The CH05 error message means you have an indoor / outdoor unit communication error. It can be caused by any of the following issues:

• No power on indoor unit
• Indoor/outdoor unit power connection error / communication line not installed
• Communication error caused by external noise
• Indoor/outdoor unit communication circuit parts burned.

Get the model number of your mini split unit (on tag on indoor unit and outdoor unit) Google hitachi error codes. You should be able to pull up a code list for that unit. I believe it may be a communication problem between the indoor and outdoor unit. Possible bad connection of wire going from outdoor to indoor unit

It's possible you have a bad data wire on one of the systems. Swap the data wire or both if two with a different wire. (1&4--2&3) whatever. Whatever you do inside obviously do outside. Might have extra resistamce that is throwing the error but will be fine for a ground wire.Or do one system at a time, being sure to change your dip switch settings until you figure out the problem unit. Good Luck!!

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I'm not sure if the thermostat is wired correctly. First, the thermostat is wired directly to the outdoor unit (compressor/condenser unit). It is NOT directly connected to the indoor unit. It connects to a low voltage control panel in the outdoor unit that sends a signal to your indoor fan/evaporator. This wire is called the fan relay switch and physically runs between the low voltage controls of the indoor and outdoor units. If the fan relay is bad it's possible that the unit runs continuously. To prevent destroying your outdoor unit there is a safety feature that prevents the indoor fan from shutting down while the outdoor unit is running. If the indoor fan did shut down while the outdoor unit was running than you would slug your compressor. That is, your compressor normally sees refrigerant gas but is instead seeing refrigerant liquid. That would not be good since this scenario would destroy your compressor. It sounds like a faulty fan relay. The actual contactor portion of the relay is in the outdoor unit.

P8 means Abnormality in outdoor unit.
Check:
1) Wrong wiring of indoor/outdoor
connecting wire
2) Reversed phase
3) Protection device is working
4) Damaged outdoor coil thermistor

Solution:
1) Check the indoor/outdoor connecting wire.
2) Change the connection of electric wiring.
3) Check the protection device.
4) Measure the resistance of the outdoor coil thermistor.
If the resistance is normal, replace the
outdoor controller board

Hope, helpful.

P8-Abnormality in outdoor unit.
1.Wrong wiring of indoor/outdoor
connecting wire.......................Check the indoor/outdoor connecting wire.
2) Reversed phase......Change the connection of electric wiring.
3) Protection device is working........ Check the protection device.(LP,HP)
4) Damaged outdoor coil thermistor.....Measure the resistance of the outdoor coil thermistor.If the resistance is normal, replace the outdoor controller board.
5) Check out door coil is cleaned. If not do it.
thanks.

Sounds like an interconnecting wiring error. Check wiring connection i.e. wires are connected in right order 1 to1 2 to 2 etc. from indoor terminal board to outdoor terminal board. Also check for slack or loose connections.
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I have had this problem with a Fujitsu unit before. If the power is supplied to the outdoor unit first but unit is meant to have power supplied to indoor unit first, outdoor will only stop when power is cut off! In that case, you will have to run the power cable to the indoor unit first and then connect from appropriate terminal back to outdoor unit. (Often the indoor will stop outdoor unit by just cutting the power to it via use of a relay on the pcb.)

check your comm board you need to make sure both are set to the same settings