GoodWe Error 12 — Internal Fan Failure / Back-Up Over Load

What it means: One code, two completely different faults, and which one you have depends on your series. GoodWe lists code 12 as Internal Fan Failure, with an explicit note that on an ES-series inverter the same code means Back-Up Over Load — the loads on your back-up output exceed what the inverter can supply. The three causes GoodWe gives sit under one entry: back-up loads exceeding the inverter maximum on an ES, an internal fan blocked by debris, and a fan cable not seated properly inside the unit.

Why does GoodWe show 12?

• On an ES-series hybrid, the total load on the back-up output exceeds the inverter's back-up rating
• Inrush from an inductive load — a motor pump, compressor or air conditioner starting — briefly exceeding the back-up capacity
• The internal cooling fan is blocked by dust or debris
• The fan cable is not connected well inside the inverter

The Pakistan factor

Both halves of this code are Pakistani problems. Dust is the first — a fan-cooled GoodWe on an unshaded wall in Lahore or Multan will pull grit through its intake for two summers and then complain. Check your own model before assuming this applies: the 8 kW and larger ES Uniq hybrids use smart fan cooling, while the 3-6 kW ES Uniq models and the whole ET / ET PLUS+ / BT range are natural convection and have no intake to block. On a natural-convection unit, code 12 is about the internal fan, not an air filter you can reach. Clear the fins before every summer, not after the first fault. The back-up half is a habit problem. Pakistani installs routinely put an air conditioner or a tube-well pump on the back-up output because "that is the whole point of a hybrid", and then the inverter is asked to start an inductive load it was never sized for. Note also that GoodWe's own guide is inconsistent about the ETU suffix on this code, so do not diagnose from the number alone — establish which series the unit is first.

How to fix it

1. Start with the load, because that is the half you can safely act on. GoodWe's first listed step for this code is to reduce loads on the back-up output. Switch off the heaviest back-up loads — air conditioner, motor pump, iron, water heater — and see whether the alarm clears.
2. Add up what is actually on the back-up circuit and compare it with your inverter's back-up rating from its datasheet. The ES and EM manuals put it plainly — reduce the back-up loads until the total load power is below the back-up nominal output power. If an air conditioner ended up on back-up because it was convenient at commissioning, that is your answer.
3. Look at inrush, not just steady load. GoodWe's system-fault table names inductive load spikes as a cause of back-up shutdown and recommends a soft starter for pumps and motors. A 1 hp pump that runs at 750 W can demand several times that for the first second.
4. If the back-up load is comfortably inside the rating, treat it as the fan. From the outside, with the system isolated by your installer, check whether the cooling fins and the fan intake are caked in dust. Clean them dry — compressed air or a soft brush. Never spray water near the heatsink.
5. Do not open the inverter to reach the fan or its cable. GoodWe's remedy for the fan half of this code is one restart, and then the service centre. There is no owner-level step that involves the inside of the enclosure.
6. Power cycle once, as GoodWe directs. If 12 returns, contact your installer or the GoodWe service centre and tell them which series you have, because that single fact decides whether they arrive with a fan or a load schedule.