dwh
Tail-End Charlie
If one panel is working and the other isn't, then I'd take Haf-E's advice and check the bypass diodes (if they're accessible) on the non-functioning panel. Properly sandwiched solar cells and wiring almost never fails - it's usually something outside the sandwich which fails. I.e., the diodes or connections.
A solar panel with failed diodes can allow power to flow backwards though the cells. That will turn the solar cells into neat little radiant heat units which will consume the power being produced by the other panel.
Also, any shade at all can reduce a panel's output. Say the panel is made with 2 strings of 32 .5v cells in series. That panel will produce 16v, but if even 4 of the cells in one string are shaded, that string will only produce 14v. If the voltage on the string drops enough to get bypassed by the diode, then that panel's rated output just dropped by half.
If that same panel has one bad diode, then the string that is working properly will produce power, which will then be consumed by the other string and that panel's output just dropped to 0.
A solar panel with failed diodes can allow power to flow backwards though the cells. That will turn the solar cells into neat little radiant heat units which will consume the power being produced by the other panel.
Also, any shade at all can reduce a panel's output. Say the panel is made with 2 strings of 32 .5v cells in series. That panel will produce 16v, but if even 4 of the cells in one string are shaded, that string will only produce 14v. If the voltage on the string drops enough to get bypassed by the diode, then that panel's rated output just dropped by half.
If that same panel has one bad diode, then the string that is working properly will produce power, which will then be consumed by the other string and that panel's output just dropped to 0.