Noticed my ICC/clearance light were not on during lighting check.
Checked fuse, not blown.
Noticed my turn signals were out also. As were the instrument lights.
Checked fuses, all good, replaced anyway.
Found that the tail light fuse feeds all of the above.
Replaced fuse, all came to life.
Also;
While bleeding my air system noticed that both gauges in cockpit still read 110 PSI with "wet" tank empty.
Check valves on the air tanks prevents front tanks from depleting when wet tank/supply line rupture or drain valve line rupture. I think would do the same if compressor malfunctions