MRCOOL / DIY 5th Generation
EH 0B error code
The indoor PCB does not receive feedback from the display board.
- Severity
- technician
- Verified
- Jul 18, 2026
What triggers it
The indoor PCB does not receive feedback from the display board.
What to do
- Power off, then restart the unit 2 minutes later; if the code clears, the unit functions normally.
- Check the wiring and connections between the indoor PCB and display board.
- Correct poor or improper connections.
- Replace the indoor main PCB.
- If the error still exists after replacing the indoor main PCB, replace the display board.
Reset procedure
Power off, then restart the unit 2 minutes later.
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
No related error-code page is identified in the sourced diagnostic.
Technician scope
Display board, PCB
Source
- Document
- data/sources/mrcool-diy5-service.pdf
- Section
- 4.7 TS07: Indoor PCB/display board communication error diagnosis and solution
- Page
- 66