Unit displays E5 and may not start compressor or fan

Safety: Turn OFF power at the breaker to both indoor and outdoor units before touching any wiring.

Steps to resolve E5:

• Verify power supply: Confirm correct line voltage at the disconnect and indoor unit (per nameplate). Low or missing voltage can cause communication errors.
• Check communication cable: On Friedrich ductless systems, inspect the multi-conductor cable between indoor and outdoor units. Ensure connections are tight and that terminal numbers (e.g., 1-2-3) match exactly on both ends.
• Look for damage: Examine the cable for cuts, rodent damage, or UV deterioration. Replace the cable if any conductors are exposed or broken.
• Reseat connectors: On both indoor and outdoor PCBs, reseat any plug-in connectors for communication lines. Ensure there is no corrosion or burnt marks on terminals.
• Power cycle: After verifying wiring, restore power and leave the system off for 5 minutes, then restart and check if E5 clears.
• Board diagnosis: If wiring and voltage are correct and E5 persists, one of the PCBs may be defective. Visual signs include burnt components or bulging capacitors. Board replacement is typically required.

Note: If you are not experienced with electrical measurements and wiring, have a licensed HVAC technician perform these checks.