microwave rotary switch contacts go bad requently

[jm1234]

Hi, I have a 11 year old microwave Siemens and the main function selector switch is a rotary type. It goes bad every few months, there are carbon (?) pads and the metal contacts that drive on them create concentric circle tracks from the residue.

I clean the tracks and the metal contacts with IPA and it works few months again. Here you can see the contacts:

Once I tried this contact cleaner: Kontakt 60 https://www.tme.eu/Document/3f58feb2...TAKT60.DTE.PDF, but it only lasted few weeks, so probably not a good choice.
Is there any more lasting solution?

[CapLeaker]

From what I see it's worn quite a bit on certain places. Chemtronics makes a carbon trac repair kit. Kinda paint over it, let it dry, done. Or use conductive paint. Cleaner won't help much here, and it's probably is too late for the leaded pencil trick.
If it would be mine, I'd take some fine sand paper and roughen the bad carbon tracks very gently. Clean with 99% IPA. Paint over with something conductive and Bob is your uncle.

[stj]

lube it with dialectric grease

[jm1234]

Thanks for all the help, I ordered this conductive lacker:
https://www.tme.eu/en/details/lak-gr...y/art-agt-022/
Will apply it hopefully this week and will also set reminder for me to report back in 6months or so.

[R_J]

Clean the copper contacts with a pencil eraser, then do what stj says, and apply dielectric grease to the contacts to prevent oxidation.

[jm1234]

fwiw, I applied the conductive lacker I linked above, but sadly it only lasted some 2 months.

[stj]

because you had no lube to stop the moving contacts rubbing at the pads.

[harp]

It is build to intentionaly worn up - consumer electronic... whenever you have soft material and hard material it not design to last... You can make etching copper pcb by yourself, it is not so complex, so it last lifetime... or, if the traces of pcb is copper, you can peel up some copper foil (from scrap pcb) and glued over existing contact, soldering it on side to traces...