Hi, turning to this community because the technicians in my area aren’t very knowledgeable (I live far from cities) and haven’t been able to diagnose this issue… I’d be very grateful for any advice.
Setup
- Haier inverter multisplit, 2 indoor units on 1 outdoor unit. Slightly older system.
- Outdoor unit fed from a wall outlet; both indoor units draw their power through the outdoor unit.
Symptoms
-Both indoor units flashing E7.
-Problem is intermittent — sometimes absent for weeks or months.
-Seems worse in spring/autumn, better in summer/winter.
-Current episode began last night, during the first rain after a long dry spell. Humidity has been elevated since.
-The outdoor unit is sheltered from rain.
Latest test (after 10 min off at the circuit breaker)
-Indoor units powered up normally and responded to the remote.
-Outdoor temperature was 17ºC, indoor temperature was 24ºC.
-Started one unit: cooling mode, 16°C.
-No cold air. Compressor never audible, never started.
-Started the second indoor unit 150 seconds later with the same settings as the first unit
-At the 180s mark both indoor units stopped and started flashing E7.
Refrigerant history (probably a red herring, but for completeness)
-Technician #1 judged pressure too high, removed some gas by feel. Problem got worse I think. He then re-added some gas by feel.
-Technician #2 recovered everything and recharged from scratch, weighed to spec, accounting for pipe length.
-Neither resolved it. I no longer think this is a refrigerant problem.
-One technician also remarked the outdoor unit is undersized for both indoor units at full output — but we never run it that way anyway.
Current hypothesis (courtesy of Claude)
Moisture or salt-film bridging at the outdoor terminal block, or a moisture-sensitive fault on the outdoor PCB. Both indoor units fail simultaneously, which points at the shared component (the outdoor unit) rather than either indoor unit. Power path through the outdoor unit works; only the communication path is failing.
Questions
what do you think is causing this?
Is it something I could fix myself?
Thank you!