You should be able to access the walker sensor on the inspection plate furthest to the back (left side). In my younger years I use to fit between the walker that was up in the back and go in between the chopper and the walker (you can also remove a plate that transfers material from walkers to chopper and get up there) but I agree if it can't be simply solved this way (usually flicking it back and forth will reset or clear out the foreign object and the light will work again. I have reworked our electronic system on the F's and F2. Works good when working! lOl