Hello all, I've got a Ryobi branded Decastar 135E, great little welder & has served me well.

problem now is that setting switches don't seem to be working, theres 2 switches, min/max & 1/2, so four settings.

it seems to be stuck on a low setting, still welding fine, nice & clean etc, just doesn't have any grunt for welding anything more that 2mm thick
flicking the switches to max / 2 ( highest setting) & nothing changes.

I've never done much welder maintenance so don't really know where to start with this....

any advice or info on this issue would be greatly appreciated