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Mysterious cause for bad electrical connection?

The other day I noticed the “third” brake light on my Corolla was out, so decided to replace the bulb. Turned out it wasn’t the bulb, just a bad connection. No corrosion visible on the bulb or socket, and just putting the bulb back in the socket made it work again. I’ve had this problem many times with flashlights, they won’t work at all, no light, and removing the batteries and putting them back again and the flashlight works as if nothing was ever wrong. Any ideas what causes this? It’s a mystery to me.

Oxide forms on the contacts, blocks the current and turns of the light. You rub the contacts when you remove and replace the bulb removing the oxidation. Voila! The bulb works. Some of the sockets have little more than point contact so it doesn’t take much oxide.


There was no oxide visibly apparent on either the bulb or the socket. The fixture is inside the passenger compartment so not exposed to the weather. The materials appeared bright and shiny as the day they were made. Could those material maybe be aluminum? I think the common oxide that forms on aluminum is nearly invisible.

Another issue can be cold flow of solder if they use those ball solder ends. Did these have the wires offset on a flange or the ball ends or?

Thats the tricky part… youncan’t always see the oxide. Rust is red and obvious. Zinc or antimony oxide looks like… zinc or antimony! Ssme for brass although it doesn’t look shiny anymore.

Phenomena is called “fretting”:

it makes a case for the special grease on the contacts to prevent oxide formation

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Fretting eh? It’s good somebody is trying to understand this problem at least. I don’t think I’ve ever had a flashlight that didn’t have this problem. I was using a flashlight today in fact, worked fine 2 days ago. Turned it on today, no light at all. Jiggling the flashlight around, knocking it with my hand, it changed from no light at all to a very dim light output. Removed and reinstalled the batteries, light output bright as before. I don’t see much in the way of solutions though, at least as applies to cars. I wonder how many man-hours are spent on this problem every year by auto mechanics, home diy’ers, appliance repairmen, and the like?

Electrical connections, particularly at a lower voltage can be a problem. My church has a digital organ that would sometimes cut out and then after turning it off, would come back on. When the organ technician came, he pulled out circuit boards and then plugged them back in. We haven’t had a problem since he did that. He told me he did that with the same make organ in another church. He did spray contact cleaner on the connections. What is interesting is that I couldn’t see any visible corrosion on the connections.
I have had the same problem with the remote control for my television. I just remove and reinstall the batteries and it works again.

I had a washing machine that behaved like that, believe it or not. I’d have to take the console apart and remove the circuit board and plug it back in again every three months. This went on for 6 years, every three months, crawl behind the machine & take the console apart. I figured this was just a push-the -rock-up-the-hill Sisyphus chore I had for some offense I inadvertently committed which offended the Gods of the Universe. Then for some reason – this whole subject seems to have an element of magic, maybe I got a reprieve, who knows?? – I never had to do it again, the machine worked fine until I retired it after 30+ years of service. Since the electrical connections worked for 25 odd years without having to do anything, it must be possible to design corrosion resistant connections. But nobody seems to know how. A conundrum for sure.

George, GM discusses fretting corrosion of electrical connectors in their Technical Service Bulletins. It’s a real thing. I’ve seen them include it in bulletins for years and years.

When one encounters electrical issues with a vehicle, doing what you inadvertently did should be the first remedy tried, that is disconnecting and reconnecting appropriate connectors. Should that fix the problem then one should apply dielectric grease, not to improve the conduction, but to prevent future fretting.

Several years ago, I permanently repaired an inoperative redundant drive-by-wire accelerator pedal by doing just what is described above. The invisible fretting was causing the pedal to throw a code for itself and put the vehicle into limp mode. The “fix” was instantaneous and many years later the problem has never returned!

I’ve always been a subscriber to doing easiest, cheapest things first when trouble-shooting. Does that mean I’m cheap and lazy? Perhaps, but I like to think of it as working smart, not hard. :crazy_face:

When applicable, cleaning contacts with a pencil eraser helps clean the invisible foe before applying dielectric grease.

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One has to wonder, if dielectric grease is a solution, why didn’t the manufacturer apply it when the car was built?

because it would cost $0.57 in materials and $3.95 in workmanship on very car they produce?
bean counting team decided it is too expensive :slight_smile:

My 45+ year old truck seems to have fewer of this type of “bad connection” problem. It uses a material that looks like brass or copper for the bulb sockets, rather than the bright shiny metal used on the Corolla and on my flashlights and batteries. I wonder if applying some dielectric grease to my flashlight batteries would work? I can see how it might on an electrical connector that is designed to have quite a bit of force between the two sides, but flashlight’s usually don’t have that much force at the connections.

I just revived a flashlight yesterday with this same exact issue. Because of this thread, I was going to use dielectric, but I got lazy like the manufactures and didn’t make the trip to the garage.

If you try the dielectric grease for flashlights idea @tcmichnorth , let us know how it works.

Dielectric grease helps, but the connections must be absolutely dry when you put it on or it will trap the moisture and lead to further corrosion. If you can find a water displacing oil that meets mil-spec VVL-800, that is the best stuff to use.

I like this stuff when contacts are a problem.

This is partly conductive so do not let it bridge across contacts, use only a tiny bit at the contact point. I find it also works in electronics where the batteries leaked and caused a lot of corrosion on one or more contacts. Brush off any loose corrosion and apply a dab to the contacts and insert new batteries. You can get it at Home Depot, a $6 bottle lasts for a long time.

Edit: this is the stuff professional electricians use.


Contact corrosion is a very common issue that most technicians are well aware of when working on circuit problems. High quality electronic test equipment use gold plating for making connections to circuit boards since gold doesn’t corrode, and like silver also, has a very low electrical resistance.

I wonder how much it would cost to gold-plate battery contacts? 25 cents per battery?