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I have this expensive DPDT switch (20A 250V 2hp) which the only problem is dirty encumbered inside. The encumbrance is made of carbonized material and some kind of wax and dirty electrical contacts. The contact poles are in good shape after a good cleanup. I cleaned all part thoroughly. Now it all look clean and neat, ready to reassemble the switch. Since, originally, there was some lubricant inside, that looked like some kind of wax, I am on the search for a similar product.

I recently dipped contacts on a relay (2HP motor) with high temperature silicon grease called Dielectric Grease 67VR. My repair lasted about 3 days (perhaps 20 ON/OFF cycles). The contacts ended up welded together and the grease was carbonated. So, obviously, the dielectric grease is Not a good option.

The Question: What kind of lubricant would be suitable in my switch so it does not end up being a disaster but rather a successful repair ? enter image description here

Fred Cailloux
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    **encumbrance** /ɪnˈkʌmbr(ə)ns,ɛnˈkʌmbr(ə)ns *noun*, **an impediment or burden.**, "the horse raised its hind leg as if to rid itself of an encumbrance" synonyms: hindrance, obstruction, obstacle, impediment, restraint, constraint, handicap, inconvenience, nuisance, disadvantage, drawback; An interesting choice of word. Is it a translation from French (Canadian)? – Transistor Nov 14 '18 at 19:31
  • I _so_ want to repost the question on interpersonal relations stack exchange :) (Sorry, just _had_ to comment that. Back to electronics now) – Stilez Nov 14 '18 at 21:19
  • can you use graphite? it won't carbonize, well any more... – dandavis Nov 14 '18 at 21:21
  • Automotive isn't especially high voltage, but at least this is a grease for switches: https://uk.rs-online.com/web/p/contact-cleaners/3375925/ – joe electro Nov 15 '18 at 04:56
  • I've refurbished a number of switches, including the century-old porcelain bodied pushbutton light switches (with mother of pearl buttons) https://commons.wikimedia.org/wiki/File:Push_Button_Light_Switch.jpg in my house, but they all were assembled with screws, looks like this one has rivets drilled out. Have you thought about how you're going to reassemble this? – Phil G Nov 15 '18 at 15:45

3 Answers3

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The defining feature of dielectric grease is that is is a good insulator, and is used to keep moisture away from contacts where it could cause corrosion or conduction. Any silicone compound will break down under arcs leaving a silicon oxide that is an even better insulator, pretty much guaranteeing damage to the contacts.

Switches should be greased with a high melting point, high viscosity grease on the pivots and sliding mechanisms only - where it will hopefully not migrate to the contacts, which should be dry.

Phil G
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  • Minimalism applies here... – Solar Mike Nov 14 '18 at 19:32
  • Phil G your explanation makes total sence. It would explain why the original lubricant was of ultra high viscosity like some kind of wax. And also would explain the malfunction caused by accumulation of that burned lubricant at the contact location. I think I will lubricate only the sliding parts and leave the contact dry. – Fred Cailloux Nov 15 '18 at 18:40
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When contacts arc they polymerize organic materials in the air. The result is a sort of crud that will cause contact failure. If you lube the contacts you are just speeding up the process. When the manufacturer lubes the mechanical parts they probably use a grease with very low “creep”. That is, the oil tends to not separate from the grease and contaminate the contacts. Not sure where you would find such a thing. Silicone grease is usually thickened with fumed silica, but some are thickened with lithium soap. Silicone does not usually make a good lubricant unless specially formulated for that. `

Robert Endl
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Cool-Amp makes "Conducto-Lube", a silver-containing grease specifically designed for switches, breakers, etc. https://www.cool-amp.com/conducto-lube

Frotz
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  • I'm not sure you'll want a grease on your contacts that tries to keep conducting after you have switched it off. – joe electro Nov 15 '18 at 04:57
  • If that's happening in a switch dosed with conducto-lube, you probably used too much. – Frotz Nov 15 '18 at 05:40
  • Bad advice. Conductive grease is to be applied to irregular / loose / vibrating surfaces which should **remain electrically connected all the time**. Putting it on a switch which opens and closes under load will quickly degrade the grease to the point it will become harmful for the switch. – Dmitry Grigoryev Nov 15 '18 at 07:43
  • "Eliminates hot spots in hinge joint switches caused by poor contact" this stuff is useful on the current-carrying hinge of large MV switches as depicted on the website.. It'd be dangerous to use on a switch like this that has a sliding contact since it'd smear out onto the insulator that moves in between the stationary contacts when off. – Phil G Nov 15 '18 at 15:39
  • There's "Lubricates switches" on the website and use on switches is mentioned in the spec sheet . Given the company has been at it since 1944, I figure they know what they're doing. – Frotz Nov 17 '18 at 01:59