It sound like you still have some resistance in the light causing it not to work when bolted up. You need to clean both sides and the earth connector. The smd's will need a good current flow as they have resistors in them as well. Even if every thing test ok with no load. As soon as you load the circuit up the resistance in the connectors is too high and won't light the bulb. Switches are a common fault for the windows. I would look at them first
The light is an easy fit. The rivets that hold the light together get corroded and need a good scrap round. Even if looks ok get a flat head screw driver and scrap it round the edge of the rivet againt the metal tracks.
This will be off the roads for a week or 2 in the next month or so. Need to get the forged 5e built and in. I've been running the 4efte engine nearly a year now. 1bar of boost, road mapped by me on emu and still going strong lol
So dragged this old thing out last weekends. Was looking rather grubby so sloshed it off. Have done absolutely nothing except take a few bits off this year. I will crack on with the stripping soon. Lots of bits to go on and change. Might even space frame the front end yet. Quick dirty pic rolling on 14's
It was only really meant for Ollie. But I got carried away haha we did fill ollies air vents up with glitter on a stop on the way back. It was well funny when he turned the blowers on.