The Cessna 120-140 Association Forum

Does anyone have any technical information about how the piano keys switches work? I have several switchs that won't function. It appears the entire panel needs to come apart to gain access.

What do you mean "won't function"

Do you mean they don't move and are not being used to switch something? If thats the case then all you need to do is remove bolt that is holding it in the "off" position and replace it with a toggle switch and use it to switch something else such as Radio Master.

The switches are very hard and stiff to move but also will not make contact internally to close the circuit. My turn coordinator and nav lights work, but will not turn on.

Ok, I suspect the toggle switches are defective. You can access them from underneath but really the only way to have full access is to remove the instrument panel ( the part that is supported by the rubber mounts) then you can see down and remove the toggle switches that are bad.

would sometimes failed switches sometimes simply be dirt and corrosion? I'm not sure, have not worked on mine yet, as so far so good on them.

But extrapolating from other life experiences, GM is known to have window switches that go bad regularly as they age, most ppl replace them. I have found that is a waste of time and money. Unhook the battery, get some 91% isoproply alchol (the active ingredient in the spray contact cleaner-just oodles cheaper from Rite-Aid than in spray form) dump some on the switches, operated them rigorously. Blow with canned air if handy, if not let them dry for a bit. Connect the battery and whammo saved the time and money of changing switches... I have done this numerous times on different vehicles and its worked far more times than its not...

Not sure if the theory could be adapted to our piano keys or not...

Ray

Just to be clear the "piano keys" are not actually switches, they just operate a normal AN3021-2 toggle switch.