how can I fix my hoover autocare 1100?

over fill is caused by pressure switch fault, not sensing. or more likely be the pressure chamber blocked .
could be a split pipe or detached pipe
remove the top of machine you will SEE pressure switch and you will SEE the plastic pipe (check as in 1)
if you follow this pipe downward you will come to the pressure chamber (check as in 2)

1)check the plastic pipe has NO SPLITS/HOLES in it
2)check the hole in the pressure chamber is CLEAR

wirecutterman
September 2009