Klarstein split AC shows E7 and outdoor unit does not start or respond.

Safety: Turn off power at the breaker and verify no voltage is present before touching wiring.

Steps:

• Check interconnect cable: Open the indoor and outdoor electrical covers. Verify that the multi-core cable is firmly connected and that terminal numbers (e.g., 1-2-3) match exactly between indoor and outdoor units.
• Inspect for damage: Look along the cable route for cuts, rodent damage, or crushed sections. Replace the cable if any conductor is damaged.
• Polarity and grounding: Ensure line, neutral, and communication terminals are wired according to the Klarstein wiring diagram. Incorrect polarity can cause E7.
• Tighten terminals: Loose screws can cause intermittent communication. Tighten all terminal screws securely.
• Power cycle: After corrections, restore power and wait several minutes for the units to re-establish communication.

If E7 persists with correct wiring and a known-good cable, either the indoor or outdoor control PCB may be defective. This diagnosis and replacement should be done by a qualified technician.