PC 40 error code

What triggers it

The main PCB cannot detect the IPM board / compressor-driven chip.

What to do

1. Check whether at least one LED in the compressor-driven chip is lit.
2. If not, check the signal wire between the compressor-driven chip and main board, reconnect, and retry.
3. Replace the compressor-driven chip if the wiring check does not resolve the fault.
4. If the system is still not normal, replace the outdoor main board.
5. If the system is still not normal after that, replace the electric control box.

Which systems show it

• MRCOOL DIY 5th Generation single-zone 9k, 12k, 18k, 24k, and 36k D25 indoor/outdoor models listed in manual section 1.1.

Related codes

Technician scope

Technician-tier outdoor auxiliary board diagnostic; see service manual section 4.3

Source

Next step