Y Axis - Not homing / moving correctly (Wanhao i3 Plus / Balco Touch)

[curious aardvark]

so what EXACTLY did you do when fitting the belt tensioner and stepper dampener.

Clearly there is a cause and effect here and obviously something you did caused the problem.

So - in mind bendingly intricate detail - what did you actually do ?
Was anything disconnected or any wires rerouted at any point ?

Have you twisted the belt ?
You would probably have needed to take it off the idler cog to fit a belt tensioner, and all it would need is a simple twist below the printbed to reverse the direction of travel.
That's probably my current favourite theory.

Did you move or otherwise fiddle with th endstop.

have you changed the slicer profile in any way ?

Something you did caused the problem. I can think of a few ways this might happen (the top one being the twisted belt) - but I'd rather you detailed what you did and we'll see if any of that fits any of my current theories :-)

[TenbagUK]

so what EXACTLY did you do when fitting the belt tensioner and stepper dampener.

Clearly there is a cause and effect here and obviously something you did caused the problem.

So - in mind bendingly intricate detail - what did you actually do ?
Was anything disconnected or any wires rerouted at any point ?

Have you twisted the belt ?
You would probably have needed to take it off the idler cog to fit a belt tensioner, and all it would need is a simple twist below the printbed to reverse the direction of travel.
That's probably my current favourite theory.

Did you move or otherwise fiddle with th endstop.

have you changed the slicer profile in any way ?

Something you did caused the problem. I can think of a few ways this might happen (the top one being the twisted belt) - but I'd rather you detailed what you did and we'll see if any of that fits any of my current theories :-)

I like the sound of that, and am going to fully agree with you on something having caused it to happen - and the most likely answer or cause for it is myself, or I should say me cocking it up in some way. It does sound like you could be onto something with the twisted belt theory, although I'll be honest and say I'm quite mechanically / physics-y deficient so I don't understand why it would be happen. I've always been more artistically inclined! With that said, I've attached some pics to see if that helps you guys decipher my cockup, and a short video of the horrible vibration my printer now causes when homing away from the end-stop on Y (the other two axis are fine).

Now, onto the What I Done:

Firstly I went over the rods for my printers X, Y and Z axis's and found numerous loose. One of the rods on my X axis was completely free floating (the horizontal one the print head moves along), and so could move back and forth freely. The difficulty with this was I was doing it in quite low light, and so was able to tighten lower X axis rod fine, using a small allen key, but I couldn't get access to the upper X axis rod without taking the printer gantry apart - or so I thought. So I took the two 'arms' off the left and right of the printer, so I could access the grub screws to tighten the upper X axis rods - then I found that there was a hole in the top X axis bracket to allow me to tighten the grub screws there without dismantling it. So that was annoying but will be conveniant for the future (maybe!). I had no difficulty tightening up the Y rods which were a bit loose, as the allen key is easy to locate in the grub screws so I did that next.
I then decided that whilst the printer was in bits I'd fit at least one of the stepper motors I had bought to see how it improved / changed things. So i chose the Y-axis, and flipped the whole printer base (detached from its gantry arms) upside down, and unscrewed one of the screws holding the belt in place. I then took off the stepper motor for Y-axis and added the dampener, I fiddled with the distance of the spinning head of the stepper motor and tried to get it to be roughly in line with where I thought it needed to be to align with the other side (you called it an idler cog but on mine it is less light a cog and looks more like a small spindle / bearing - unless i'm getting the terminlogy mixed up and the idler is on the stepper itself). I lined it up and tightened it down, and then tried to re-fit the belt - where the belt tensioner had fallen off with my fiddling. I re-attached the belt, and then with pliers managed to put the spring belt tensioner back on the belt (although I dont quite know where it was originally positioned). I then moved the bed by pulling the belt and found the spring tensioner bashing into and trying to 'go around' the stepper motor so I had to relocate it to where it wouldn't hit either side of the 'ends' (either the idler side or the stepper motor side). I managed to find it a place to fit where it doesn't catch on anything. I did think to myself whilst doing this that whilst it was flipped upside down, the bed was resting on the floor, and thus was constantly having a bit of movement as I was fiddling trying to get the belt back on. I wonder whether this might have caused some of the issue?
I then rebuilt the gantry, with a bit of fiddling, and got it back together. I then went to check the printer and found the issues that I am now describing, with the printer bed wanting to move away from the end-stop instead of towards it on the Y-axis. I did manage to get the printer to a place where I could print, but as you should see from my screenshot it has printed the dial 'flipped'. The screenshot with the two dials are from before and after, the left dial is before I added the dampener, and the right is after.

Any help you can put together from my wall of text and pictures would once again be very appreciated!