XYZ Davinci Issues

[-fred-]

Hello, First post here, trying to get some info on an xyz davinci 1.0 which is causing me no end of headaches. The latest one is that it thinks the top door is open all the time. This is after I tried using 3rd party filament in it, which having looked online I found someone else had the same issue, so I'm wondering if it's a software thing rather than a faulty switch? Anyway before I realised this, I went and cut the wires to the switch, hoping to bypass it, however after I cut them (they were behind a plastic cover) and brought them into the open I found I had gone through three wires, not 2 like I was expecting. I've since verified that they all go to the switch. I've tested them and I can see there is one 5V feed, one earth (NOT ground, I'm from England), and a third wire which doesn't seem to have any current through it. I believe I've tried every possible combination of connections but it still thinks the top door is open. So, in summary - how should the wires be connected when the lid is shut? Once I know this I'll connect them up, bypassing the switch. Then, assuming that doesn't solve the error (don't think it will as I've already tried every combination) what is causing the top door open error? Does it need a new firmware? Thanks in advance! Fred P.S. This is just the latest in a long line of issues I've been having. I'm considering swapping the whole board out for a RAMPS conversion, but trying to avoid that if I can help it.