Electrical issue

Hi. About a month ago, all wiring was removed from body / bulkhead / chassis for a few repairs on the bulkhead, and for a restoration on the chassis. All that is now done, but come to put it all back together, i'm starting to think i'm a bit out of my comfort zone. I am at the stage where i am putting the dash back together, but come to checking stuff up again, lights, and the blower switch all seem to go to the glow plugs light symbol on the dash, without acutally activating them, and the instruments themselves don't work. What's going on? is it simply an earthing issue, or do all electrical systems need to be put in for these things to work? Help!

Thanks