What you will see
- Inverter will not start in the morning after rain or heavy dew
- Code 39 clears by late morning
- Code 39 stays even on dry days
Why it happens
Before connecting, the inverter checks that the panels and DC cables are well insulated from the frame and earth. Water in an MC4 connector, a cracked cable or a damaged panel backsheet lowers that insulation.
On hybrids, damaged battery cables or loose battery terminals can also cause it.
Diagram
Damp morning, weak insulation
Dry day
Panels and cablesWell insulated
→InverterStarts
After rain or fog
Wet connector or cracked cableLeaks to earth
→InverterWaits, code 39
If code 39 stays on dry days, there is likely damage to find.
What you can check yourself
- Note whether it only happens on wet or foggy days
- From the ground or a safe roof, look for cables lying in water, chewed by rodents or rubbing on sharp metal
- Check again on a dry sunny day as Sungrow advises
What not to do
- Do not unplug MC4 connectors or open DC isolators
- Do not spray water on the panels or cables to test
When to call us
- Insulation test each string and the DC cables
- Inspect connectors, junction boxes and cable runs for water ingress and damage
- On hybrids, inspect the battery cables and terminals
Monsoon and winter fog
Code 39 rises across Punjab in the monsoon and on foggy winter mornings in Lahore and Faisalabad. We test each string to find the wet or damaged section.
Send us
fault screenshots with times and weather, and photos of the cable runs on the roof