According to the solar controller's indicators, the panels aren't generating power (aka it's dark). No indicators showing an abnormal condition.
There are but 2x100w panels wired in series. When the panels are dissed from the controller there is 38-41v dc present across the cables to the controller, at the controller. Panel spec says open circuit is 22.9v (Suspect that this is a max value?). So that reading seems reasonable.
Dissed the panels from the cabling to the controller, (so using the connectors supplied fitted to the panels) and tested using a 12v 10w bulb. Both panels lit the bulb brightly, even on an overcast day.
The only way I can think to apply a load at the controller end of the cables is by wiring 3x12v bulbs in series. Fiddly soldering.
All was installed, by me, last summer (the 4th install of this kind that I've done) and was working as it should when we left the boat for the winter.
Controller is (German made) Votronic. Tried a replacement to no avail.
Anyone give me a clue as to what might be going on, please ?