The HASCO part is a DC power relay
--I got that by Googling the part number you supplied. But that's just one component in a black-box device that is labeled on one side--barely readable in the photo, but I think
it's a photovoltaic control module. Does it click at night? If not, that's probably what it is.
If so, the clicking relay suggest that it's an old-tech, very inefficient "on/off" type controller. Replace it with a modern MPPT controller such has Victron's Smart Solar 75/15
, and you'll get significantly more power out of that panel--and with no clicking!