Corroded connection

[PlainName]

Tracked down a problem with our electric gates to a dodgy connector, photo attached. Annoyingly, there were zero issues with this actuator until I 'fixed' it after having to replace the bearings on the other actuator. Since I had the parts and recent memory of a teardown, I decided to replace the bearings in this one as a preventative measure (they turned out to be just on the verge of a slow death). After that it's had this intermittent fault, so of course I assumed it was something I had done during the repair and I've since re-repaired much of it, including replacing all the microswitches, etc.

Just for the hell of it I did previously dismantle this connector to clean up and spray with contact cleaner, but obviously that wasn't awfully successful. So how should I got about making this a more permanent repair? Replacing the contacts would be a last resort (since I don't have any suitable, and it would mean shortening the wires).

AFAICT, despite the wire thickness it is a very low-power circuit, which may be why a little resistance causes the problem.

[GLouie]

I would try cleaning the connectors up and doing like the automobile manufacturers do - enrobe the connectors-contacts in electrical connector grease such as Nyogel 760G. This is also rebranded and sold as a part from major auto manufacturers and usually much cheaper there. TDS attached with auto manuf. part numbers.

Nye Lubricants provides all sorts of documents swearing this stuff is a godsend. It is not a silicone. I would guess there is similar stuff made by other manufacturers.

[TimNJ]

If the contact plating doesn’t look totally shot, maybe you can just salvage the existing contacts. Submerge it in DeOxit D-series cleaner. Every couple of minutes scrub it with a stiff bristles brush until the crud is loosened/dissolved/chemically converted.

But, if the contacts already have serious fretting/galling damage, there might be little use in trying to re-use the old contacts, if your goal is long term preservation. In this case, install new contacts.

I use DeOxit L260 grease on some contacts which are subject to vibration, repeated plug/unplug cycling, and/or corrosive/humid environment.

[PlainName]

Thanks for the ideas. I had to get something done so used a contact cleaning block to get rid of the surface stuff (at least on the pin part). I'd previously used a soda solution to remove active corrosion, but it looks like that wasn't too successful. Anyway, a squirt with contact cleaner didn't do much - I could push the parts together outside the block and replicate the issue, so I then added a small dab of silicon grease and that fixed it!

Except... got it all together and now can't program the gates. Either the fix has made things terribly worse or I've blown up the motor position sensor when trying this stuff. Haven't had time to get a scope on there yet to see which it is. With a bit of luck I simply forgot to re-connect a different connector, but these gates seem to have it in for me.

[Ian.M]

You probably need to do something to clean the inside of the female contact.  If contact cleaner + scraping with a toothpick or shaved down match stick isn't sufficient, you'll have to resort to harsher abrasives.

A spill of cartridge paper + some metal polish is likely to be the best bet, though metal polish on a match stick that has been shaved down to fit may also be helpful.  For larger contacts, a small split wooden skewer or whittled peg with a short strip of cartridge paper through the split to carry the metal polish may be more effective.   After polishing, *ALL* traces of metal polish must be removed by solvent washing + wiping with a paper spill.

[PlainName]

Thanks. I will give that a whirl if it turns out to be the problem, still.

[No.Mad]

You could also try paste with vinegar, salt and flour. Mix 1/4 cup salt, 1/4 cup flour and enough vinegar to make a thick paste (in this proportion, you can make smaller volume), leave it for some time and then rinse it with water, then isopropyl alcohol (takes out sneaky water leftover). Weak acid in vinegar helps loose up copper oxide. You could try to use foam q-tips or earings  hole cleaners (wierd what you can fing on Amazon xD )

For contact try using grease with carbon or silver, for instance MG Chemicals Carbon Conductive Grease. You can get it from Farnell/Mouser/DigiKey or Amazon.

On other note, silicon grease you used might get somwhere where is not supposed to be, try cleaning it out with IPA.

[PlainName]

Thanks for those ideas too 

I got the scope on it again this evening and the problem is definitely poor connection, but I think a different pin. Or pins. Frankly, I am getting fed up with this one (this is the fifth time it's been apart so far) and am tempted to just solder the wires together. That's not such a big bodge as first appears - the connector is only needed for manufacture and maintenance, but most of the maintenance (such as removing the gears for lubrication or changing bearings) can be done with the connector intact. Where that isn't possible, the exit gland can be removed and the harness pulled through. And yet...

A midway would be to use something like a chocblock (using the existing crimped pins as ferrules) - horribly ugly but there are a couple in the junction boxes en route to the controller, and there has been zero problems with those since installation. Of course, I could use a similar (but incompatible) connector and then worry that the issue will return next time the bearings go. Hmmm.

[Ian.M]

I'd be wary of using salt + lemon juice or vinegar to clean electrical connections as it works by the rather weak citric or acetic acid liberating a very low concentration of hydrochloric acid from the common salt, which then attacks the metal oxides and other metal salts that compose the corrosion.   The equilibrium is heavily weighted towards the salt and citric or acetic acid side of the balance rather than hydrochloric acid and sodium citrate or acetate, (and of course its complicated by being ionic chemistry in solution rather than a molecular equilibrium), but as long as there is any metal for the hydrochloric acid to attack, forming less soluble chlorides, the solution will continue to generate traces of hydrochloric acid. 

Where does this get us for cleaning corroded metal?  Well its effective on solid accessible copper alloy surfaces, where the residue can easily be neutralized and removed, but acid chlorides are known to cause serious pitting corrosion problems for copper alloys. In fact the resulting copper chloride is itself an etchant, commonly used for PCB production. 

As such it is extremely unwise to use these mixtures or any others containing salt on small crimp contacts as the risk of some wicking up into the stranded wire and continuing to corrode it is extremely high.