The International Cessna 170 Association

New install KY 92 comm(720 chl) over a decade ago.

One knob feels slightly sticky. Radio has seen very little use.

I asked avionics guy to lube the mechanical rotating switch part.

Purchased new with understanding contact surfaces were GOLD plated. Longevity.

The Independent technician is a survivor of original shop that I had purchase/install.

I sensed a little fear in his response. Well maybe I should say strong reluctance.

One statement was " If I spray contact fluid on the switch the fluid will cause the plastic portion of the switch to deteriorate." Very surprised by that statement.

Is it safe to forcibly turn the one sticky knob?

What is really going on in servicing aged avionics?
Please advise.

GradyB, DO NOT spray contact cleaner on it!!!!! I say that from experience, sprayed a ADF and it completely locked up lucky enough the radio shop had just removed one and I had to buy it to fill the panel. expensive learning curve. Ron

If the solvent effects the plastic you will have a problem. It is doesn't you won't. No one knows what solvent might be in your spray of choice nor does the average person know what plastic makes up the radio parts. Probably several different plastics actually. If you can find someone who has actually strayed a product into your exact model and it's not caused harm or visa versa, then you would know what to do.

Safest thing is to do nothing.

An adventurous type who might throw caution to the wind would squirt something in there. I'd edge my adventuring reckless ways and use WD-40 or a pure silicone spray very sparingly. Your not cleaning the contacts. They are not likely making the knob stick. Likely the white grease applied during assembly is getting gooey.

Disassembly of the unit to minimize spray on plastic not necessary and direct application and or cleaning of the effected part might be prudent.

Many avionics gearing get "sticky" or reluctant to operate due to dirt. A clean toothbrushing directly on the gearing will usually resolve the issue. Cleaning sprays are NOT a good idea unless the avionic mfr'r specifies the product. Most lubes will attract dust and cause the problem to repeat. The only "universal" gear-lubricant I've seen recommended by the shop I trust is ordinary paraffin such as "Gulf-Wax" lightly scraped onto metal gears. Plastic or nylon gears should only be brushed or blown clean.