I don't know how old your P-19 is, but mine (1994, #779) had the 'standard'
wiring from IM with the <inadequate> 3 circuit panel on the starboard side
with the battery beneath the stove. The ground 'buss' where all of the
negative leads collected was a terminal strip with a solid copper wire
soldered to a number of terminals which then had 'fast-on' style automotive
connectors for each wire with a 10 gage wire going to the negative terminal of
the battery. The overhead light was fused directly to the battery bypassing
the circuit panel. As I remember; one of the circuits was grounded improperly
and acquired it's ground through the running lights <read that 'it wouldn't
work if the running lights were turned on'>. I re-ran all the grounds to the
barrier strip connected to the negative terminal of the battery and replaced
the 3 circuit panel with a 6 circuit Hella from West Marine that fits in the
same opening. Everything now works and is controlled via switches on the
circuit panel.
Bill de Ment P-19 #779 'Wind Shadow' ( now in Silverdale, Wa)
Eagle, Idaho