I'm trying to solve a problem with my car's fuel sender unit not working properly. I noticed there's a lot of (what I assume is) dielectric grease in the socket connecting the sender unit. Some sites I've read online advise not to put the grease in the sockets themselves, but the information is a bit vague.

Should I remove the grease from the sockets?

  • No, this grease keeps out moisture witch causes corrosion. – Moab Sep 21 '19 at 18:57

Dielectric grease keeps out water etc, but it is also an electrical insulator.

The problem with plastering it all over the outside of a connector is that when you unplug the connector, some of it gets on to pins and into the sockets, and then causes bad connections.

The best plan is to remove as much of it as possible before you unplug the connection. Cleaning the electrical contacts may be difficult, because the main purpose of the grease is NOT to dissolve in or mix with any liquid it is likely to come in contact with!

There are "industrial grade" cleaning fluids that work, but you won't be able to get those easily and using them incorrectly is a serious health hazard.

The best option is probably "rubbing alcohol" (US name) or "methylated spirits" (UK name), but note that while a product sold as "meths" should contain at least 90% alcohol by volume, "rubbing alcohol" may be as low as 70%, so search for a brand with the highest alcohol content you can find.

"Absolute alcohol" which is at least 99% pure is an even better option, if you can get it. Try a pharmacist, if you can't find it for sale anywhere else.

Note: these products may contain either ethanol or isopropanol (isopropyl alcohol). For use as a cleaning fluid, the difference between the two doesn't matter.

  • Great answer. Related question: does isopropyl alcohol leave behind any substance/residue/film on the surface which it is being used to clean? I like to use 91% isopropyl alcohol to clean electrical connectors, but sometimes I wonder if anything is left behind after the alcohol evaporates. – sam Sep 21 '19 at 20:05
  • Thanks! Yes, unfortunately it seems the grease is inside the plug. It's definitely on the pins and I suspect it might be the cause of my issues. Would generic electrical contact cleaner work to remove it? – MeltingDog Sep 21 '19 at 23:38
  • @Sam No, alcohol evaporates completely. Just avoid any brands sold for medical use with "extra additives" in them. The basic stuff is just alcohol, distilled water, and nothing else. Incidentally, "absolute alcohol" is sold as 99% pure not 100% because it absorbs water from the atmosphere - if you really need it "100% pure" for some reason in a science laboratory, you have to prepare it and use it immediately. And the reason for using isopropanol instead of ethanol is because it's easier to separate the last 1% of the water from isopropanol, if you really need to do that. – alephzero Sep 22 '19 at 1:49
  • @MeltingDog It won't do any harm to try, but if it was that simple, there wouldn't be so many posts on different web forums asking how to clean it up when it's in the wrong place. – alephzero Sep 22 '19 at 1:55
  • @Sam … If you spill beer, wine, etc on something, the residue isn't the alcohol and water content, it is mainly the sugar that was dissolved in the drink. – alephzero Sep 22 '19 at 1:57

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