Pioneer A-109 input selector trouble

[peterinbrussels]

Hi all,
Pioneer stereo amplifier A-109. When I turn the input selector, the indicator light jumps back and forth from 'CD' to 'Tuner' to 'Phono', etc. in a kind of haphazard way, not following especially the movement of the knob. To put it on a particular setting I have to turn the knob and watch the indicator light as it moves back and forth and eventually hits the setting I want. Other than that, the amp is working perfectly.
Any ideas?
Peter

[jazzfish]

try some contact cleaner on the switch. a bad ground connection could cause that erratic action