Sonsivri

My multimeter (Axiomet AX-105) after years of reliable work started to show incorrect unstable values of low resistance. The reason was - old lubricant over contacts of rotary switch.
After cleaning by alcohol a good contact is back and becomes even better than was new - typical 0.1 Ohm value of short circuit now is 0.0 almost all time.
But I think that purpose of lubricant is a protection of contacts from abrasion.
What is your experience or knowledge?
What kind of lubricant do you use as a replacement of aged one? Is it easy accessible?
Or do you simply leave it dry without further sad consequences?

Any decent meter, including an old analog one with a galvanic movement, can be zeroed out and should be, for leads' and contacts' resistances.

That said, unless someone knows of something better, there's a conductive grease that typically is used to protect lead acid battery terminals from corroding and from acid exposure - I'm guessing that MAY work.

The lubricants are often helpful in preventing corrosion as well as fretting. 

This can work for cleaning (but it sounds like you got it clean) http://www.amazon.com/CRC-05101-QD-Electronic-Cleaner/dp/B000CCMLD0

I think this might be what solutions is talking about http://www.alliedelec.com/mg-chemicals-846-80g/70125869/?mkwid=sabYU23qn&pcrid=30980760979&gclid=CNSTt4iNgMoCFQ9afgodXnQJPQ

But honestly I'd personally use non-conductive grease like a silicone / dielectric grease (http://www.adhesivecentral.com/cgi-bin/commerce.cgi?preadd=action&key=LT-37535-BP&gclid=CMTRy_KNgMoCFUWVfgodF1wBBA)

That said these are primarily used to exclude moisture and oxygen from the connection.  I've not seen grease used on the wiper contacts of any Fluke meters I've ever used.

Also bear in mind if the hard gold or hard tin coatings have worn off the wiper or PCB then it will be forever difficult to clean and keep working because contact abrasion and fretting will be more prevalent than it was when the original coatings were present.

If shorted Ohmmeter indicates form 2 to 120 Ohms depending on light touches to the switch knob and indication changes in time itself that is not the case for trimming/zeroing.

Conductive grease spread over dielectric surface of board between exposed contacts looks irrelevant. I am pretty sure - it is not applicable here.

I used that lubricant for my old multimeter without problems
http://www.wurth.co.uk/technical-chemicals/lubricants-and-rust-removers/lubricating-grease/hhs-grease-400ml

I suppose that you use one from reserves on your shelf. How long do you use the multimeter after application of that lubricant?

3 or 4 months.
I gave the multimeter to a friend he works with car electronics, i think he still use the multimeter.
The lubricant i got from the same friend

Silicone Dielectric Grease is preferred.

Use Caig Deoxit

See TechNote 012 from Kron-Hite (They make serious references, based on dial wheels)
http://www.krohn-hite.com/htm/technotes/technical_note.htm#Technical%20Note%20#012

Caig DeoxIT D5 for cleaning
http://store.caig.com/s.nl/it.A/id.1602/.f

Note PreservIT is now : DeoxIT® Shield , for lubricant after cleaning
http://store.caig.com/s.nl/sc.2/category.192/.f

Nice reading about the productlines
http://store.caig.com/s.nl/it.I/id.22/.f

Mega32

I have had good results with Cramolin (now called Deoxit) products:

http://store.caig.com/s.nl?sc=1&category=&search=cramolin

Deoxit works great for my multi-meter rotary switch, phone jack, Ethernet jack, RF connector, and power adapter connector contact,  especially for old instrument switch contacts. --highly recommended.

Hi

I use this cleaner for contact clean for many years - proven to do the work

http://www.maplin.co.uk/p/servisol-super-10-switch-contact-cleaner-200ml-jp17t

All the best

Bobi

Isopropanol with a little white mineral oil works also good.

I found "KONTAKT CHEMIE Kontakt Gold 2000" as an ideally targeted solution though the cost is higher (14euro/200ml).
(http://uk.farnell.com/productimages/standard/en_GB/81781805-40.jpg)

http://www.crceurope.com/wwwcrc/tds/TKC3%20KoGold2000.pdf
General properties and applications:
KONTAKT CHEMIE Kontakt Gold 2000 is a long-lasting and temperature-resistant lubricant.
The synthetic oil forms extremely thin layers with minimum influence on the contact
resistance of electrical contacts. The lubricant has proved to be particularly effective for
contacts with surface coatings of soft metals, e.g. gold, silver, tin. The corrosion-inhibiting
effect of noble-metal coatings is improved considerably because they are no longer
scratched by mechanical loads and vibrations.

KONTAKT GOLD 2000 "Protective lubricant for metal-plated contacts" is referenced in technical data sheet of another product:

KONTAKT 61 Contact lubricant & corrosion inhibitor:
http://www.crceurope.com/wwwcrc/tds/TKC3%20Kontakt61.pdf
1. GENERAL DESCRIPTION
Mineral oil based contact cleaner for all types of electrical contacts.
Cleans, lubricates, displaces moisture and prevents corrosion.
4. DIRECTIONS
<...>
To reduce the wear and tear of soft noble metal (coated) contacts, we do recommend the
use of our synthetic contact lubricant KONTAKT GOLD 2000.
<...>

Just have cleaned and reapply "KONTAKT CHEMIE Kontakt Gold 2000". After 11 months resistance of contacts rapidly becomes much worse than zero - about 30 Ohms changing by tens from rotation to rotation.

OK good to know... perhaps the issue is that the Gold 2000 is just a conductive lubrication but does not address the oxidation that was present which continues to degrade.
Were the contacts first treated with something that removes oxidation?

Gold 2000 corrosion inhibitor means that it slows / stops additional but didnt address the original existing condition?

Multimeter has "gold" contacts on PCB and bronze sliders. There are no signs of corrosion on both. And I used only isopropanol for cleaning that I believe does not clean oxidation. What I noticed before cleaning - grooves in the layer of old lubricant that looked thickened. Maybe I sprayed too much, do not know.

It definitely does not address to remove initial corrosion, as I understand description (see above in this thread).

The main target of using lubricant was to protect "gold" layer on PCB from abrasion. Ten months of usage before reapplying is not perfect at all but still does not bother me yet. Will see next year ;)

I used a lot of faith with succes this type of special grease for conact electric moving made by SIEMENS type WAHLER FET T.
I did not have any more or could find some

It's likely a losing battle.  The original plating on the contacts may be gone (I realize you said it was not) and corrosion may set in MUCH more quickly now.  Also there could be pitting, or loss of spring force on the contacts as well.  I've never had these things work "like new" after cleaning and lube.