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ContinuousWave: Small Boat Electrical
|Author||Topic: Dielectric Grease|
posted 01-06-2007 11:34 AM ET (US)
Dielectric grease is a nonconductive grease. Because it is nonconductive it does not enhance the flow electrical current. Electrical conductors should not be coated with dielectric grease prior to being mated. However, dielectric grease is often applied to electrical connectors, particularly ones which contain rubber gaskets, as a way to provide a nonconductive lubricant and sealer for the rubber portions of the connector.
The widest use of dielectric grease is in high-voltage connections associated with spark plugs. The grease is applied to the rubber boot of the plug wire. This helps the rubber boot slide onto the ceramic insulator of the plug. The grease also acts to seal the rubber boot, while at the same time preventing the rubber from becoming stuck to the ceramic. Generally spark plugs are in located in areas of high temperature, and the grease is formulated to withstand the temperature range expected.
Another common use of dielectric grease is on the rubber mating surfaces or gaskets of multi-pin electrical connectors used in automotive and marine engines. The grease again acts as a lubricant and a sealant on the nonconductive mating surfaces of the connector. It is not recommended to be applied to the actual electrical conductive contacts of the connector.
posted 01-06-2007 05:05 PM ET (US)
After cleaning all my electrical contacts and re-installing them i covered the exposed areas and have not seen a bit of corrosion in 14 years,,so would its use on the outside of a conection keeps any stray electric contained ???
posted 01-06-2007 08:26 PM ET (US)
The grease is nonconductive, but its really soft and gets out
of the way. I've used in a number of damp applications with
NO problems. And I put the grease on FIRST, then made the
posted 01-07-2007 01:13 AM ET (US)
The application of any sort of a nonconductive grease to the actual contacts themselves can't help them make better contact at that point. You have to hope the grease gets squeezed out of the way so the two conductors can make contact. Any grease left in there is going to reduce the contact, not improve it.
If the contacts are not perfectly clean, you'd be better off using something like WD-40 on them. WD-40 is designed to restore electrical contacts. It is a decent solvent and will get rid of a lot of corrosion and dirt in the contacts.
If the contacts are open and exposed to the air and water, it may make sense to apply a grease covering to them after the connection has been made. The grease then just acts as a sealant to keep out water and air, and may prevent corrosion from occurring.
posted 01-07-2007 04:21 AM ET (US)
Nobody's saying the dielectric grease helps it MAKE better
contact, we're saying it helps it KEEP better contact.
And practical experience says it does get out of the way
(it flows at way less PSI than a good electical connection
Two areas on my whaler that were problematic without the
posted 01-07-2007 10:55 AM ET (US)
The high temperature properties of a nonconducting grease like "Tune-Up Grease" sold at automotive supply stores make it a good choice for acting as a sealant to keep water out of lamp sockets. An incandescent bulb can create considerable temperature rise in an enclosed lamp compartment. Using a grease that does not turn into liquid and run out would be helpful.
As it happens, this week we did some service on a large uninterruptible power supply (UPS) at work. This monster has 40 batteries in series, all connected with very heavy gauge cables. We replaced one individual battery. All the connections between the battery terminal lugs and the cable crimp-on lugs were smeared with grease. I asked the technician from the UPS company about the grease. He said it was a conductive grease.
You often see a conductive grease applied to electrical connections where there is a large surface area and lots of current. If you are putting a grease right on the connection itself, it should be conductive.
posted 01-07-2007 12:53 PM ET (US)
The standard dielectric grease is Dow-Corning #4. It's rated
to 392F (200C). It stays put just fine in my light fixtures.
So does Dow-Corning 111, which I like because it's stiffer
and more waterproof.
posted 10-26-2008 02:41 AM ET (US)
What dielectric grease is best for heat dissapation?
I installed some 65/100 watt headlamps and the connectors fried.
posted 10-26-2008 06:40 AM ET (US)
I haven't had any problem applying dielectric grease to contact surfaces. As Chuck said, it will be pushed out of the way of the mating surfaces where they contact each other, and what remains will fill gaps where the conducting surfaces weren't going to meet anyway, which is exactly where you want it - pockets ripe for corrosion.
However, I will concede that to work this way, there needs to be a certain minimum contact-to-contact force. You would not use it on conductors thinner than #16 or so, and their associated connectors.
posted 10-26-2008 09:04 AM ET (US)
Dielectric grease isn't going to help heat dissipation.
A lot of the electical system in today's cars is very carefully
posted 10-26-2008 11:22 AM ET (US)
I am surprised. A 65/100-watt is not much power. In a 12-volt system a current flow of only 54-milliamperes is needed to provide the power.
: a nonconductor of direct electric current
Again, application of dielectric grease to a conductive surface will not improve the flow of current. The thermal conductive properties of dielectric grease are generally not considered.
Connectors usually "fry" because their contact resistance is too high, creating a voltage drop across them. The heat created tends to increase the resistance, and the result is more voltage drop, thus more heat. You cannot lower the contact resistance of two metal contacts by applying a nonconductive grease to them.
posted 10-26-2008 03:26 PM ET (US)
Jimh, you slipped a decimal point somewhere.
100W at 12V is 100/12 = 8.33 amp.
posted 10-26-2008 09:59 PM ET (US)
I hate to admit it, but I've been using a light amount of Petroleum Jelly on light bulbs for years. On my incadescent lights on my old trailer and on my running lights on the boat as well. I even use it on my exterior flood lights and interior bathroom lights at home (no I don't have an exterior bathroom). It always allowed for them to be easily removed and seemed to make them last a lot longer. In addition, I never had the corrosive dryness that I had before using it. Does PJ offer a nonconductive property?
posted 10-26-2008 11:27 PM ET (US)
Chuck--65/100 = 0.65-watt.
posted 10-27-2008 08:27 AM ET (US)
He means 65 watt on low beam, 100 watt on high beam.
posted 10-27-2008 09:39 AM ET (US)
My marine electrical expert said that dielectric lubricant should ALWAYS be used on the 4 pin connector for my trailer lights. I understood him to say it prevented rust and general disintegration of the components on both sides of the connection.
I apply it sparingly and my pins look great compared to my neighbor who does not use it. I have never had a problem with it. I clean up residue from time to time, clean the pins and apply a new coat.
Is this a non sequitur?
posted 10-27-2008 07:57 PM ET (US)
I slather the stuff on my trailer wiring connector also. Works great. Too bad the truth is out though, 'cause it probably won't work anymore.
posted 10-27-2008 08:13 PM ET (US)
"Too bad the truth is out."---You mean the truth that dielectric grease is a nonconductor? The purpose of dielectric grease was described in the initial article in the thread. Let me repeat it:
"...dielectric grease is often applied to electrical connectors, particularly ones which contain rubber gaskets, as a way to provide a nonconductive lubricant and sealer for the rubber portions of the connector."
Dielectric grease is a nonconductor. It doesn't improve the electrical connection between electrical contacts because it is a nonconductor. It can be useful as a sealant. I don't recommend it in open areas like a trailer where the grease can attract and hold dirt and other contaminents.
|Tom W Clark||
posted 10-27-2008 08:32 PM ET (US)
The point has already been made, at least twice above, but let me repeat it:
Dielectric grease, while not promoting conductivity, does help to preserve it by reducing conductivity degrading corrosion/oxidation of electrical connections over the dimension of time.
posted 10-27-2008 10:21 PM ET (US)
Thanks Tom and Chuck, for your clarifications. I will continue the use of this product, whose benefits seem clear. I was concerned when I read:
"Electrical conductors should not be coated with dielectric grease prior to being mated."
From your responses, it does not appear that I am harming anything.
posted 10-27-2008 11:05 PM ET (US)
I have used DC#55 for years on o-rings. DC#4 has been good as an assembly lube for tight rubber bushing and other gaskets that simply compress into place. I have run into trouble if I lube up a gasket and have to tighten/twist together. This very often causes the rubber to shift and creep out from under the unit.
On ships form all corners of the globe, I have seen grease(s)commonly used to keep corrosive elements and air from reaching the posts on batteries, but these are always applied after the terminals are installed on the posts.
I suppose the pressure and movements associated with the installation or mating of a connector or bulb base could clean all but the thinnest layor of grease off and allow current to flow, abit with higher resistance. As it was addressed, the real benefit is the barrier to contaminates that is pushed up at the edges of the connection.
I have also used Thomas & Betts Kopper Shield as a conductive antisieze. When used as a barrier between the copper ground strap of a SSB Radio Coupler and the steel hull (outside), I have noticed a complete retuning is often needed. I believe that this is adding a little bit of Capacitance to the coupler at the ground, but since I am repairing this due to some issue anyway, My repairs often have the same requirement. For a DC circuit, the capacitance won't matter. Two meter probes coated and pushed together show 0 Ohms resistance. I have pulled apart some of my connections done in this manner after 5 years. I have found that the outer edges will have turned green, but the compressed portions will be slightly darker than the copper color fresh from the can.
posted 10-28-2008 12:08 AM ET (US)
O-rings should always be lubricated prior to assembly so
the O-ring doesn't deform. Doesn't hurt to put a bit of
lube on the surfaces it contacts as well. It doesn't take
much, just enough to make things shiny.
I deal with critcal O-rings on a weekly basis with my
Also, don't use silicone grease on silicone O-rings. It
posted 10-28-2008 07:51 AM ET (US)
"Too bad the truth is out."---You mean the truth that dielectric grease is a nonconductor? The purpose of dielectric grease was described in the initial article in the thread. Let me repeat it:
Nope. This one:
"Electrical conductors should not be coated with dielectric grease prior to being mated"
posted 10-07-2009 06:39 PM ET (US)
I would agree with Newt, I used dielectric grease on the electric plug to a new wheel hub on my car and it wasn't getting a good enough connection and caused the dash lights (TRAC, ABS, CHECK ENGINE) to come on till I cleaned the grease out of the plug and re-fitted it.
posted 10-07-2009 06:40 PM ET (US)
I meant I agree with Jim, sorry!
posted 12-23-2009 10:19 AM ET (US)
If you need a grease for a contact surface their is carbon conductive grease available. It is recommended for solenoid, relays, switches, plugs, jacks and more. Putting a dielectric (non-conductor) on a contact surface will in the long run be counter productive.
posted 12-24-2009 07:37 PM ET (US)
If your conductive grease migrates, it can cause a short
between adjacent pins. That will not happen with dielectric
The force of the connection is sufficient to displace the
From past experience: MUCH less problems using dielectric
posted 12-25-2009 10:19 AM ET (US)
As its name implies, a dielectric grease is a grease whose principal feature is its ability to resist conducting electricity as much as possible, and the property of being non-conductive is what makes dielectric grease useful. Dielectric grease does not help the contacts in an electrical connector conduct electricity. Its only chance to help the connection maintain an electrical contact is by preventing other contaminants from reaching the contacts.
Slathering dielectric grease everywhere onto electrical connectors before you mate them may or may not yield an improvement. Typically the manufacturer of the electrical connector has an opinion about where dielectric grease ought to be applied and often gives this information. For example, some water-resistant electrical connectors contain rubber bellows or seals intended for the purpose of preventing contaminants from reaching the electrical contacts, and in some cases the manufacturer recommends applying a light coating of dielectric grease to those seals. However in some cases grease is not recommended. I'd heed the instructions or recommendations of the connector manufacturer.
In regard to 12-volt DC electrical systems, there is little reason to use an expensive dielectric grease to protect electrical connections because the system voltage is so low that practically any grease will have sufficient insulating properties. A very small tube of dielectric grease costs $5 because the grease it contains has wonderful electrical properties that permit it to remain non-conductive in circuits like a spark plug electrode where voltages of 20,000-volts may be present. It is not necessary to employ such a skillfully formulated grease to keep moisture from the terminal of a 12-volt battery. Indeed, it is common that general purpose marine grease can be used as an electrical insulating grease in 12-volt systems. For example, in the operating instructions from one outboard engine manufacturer, the following procedure is presented for making electrical connection to the battery:
IMPORTANT: Make sure all components are clean and
Connect the RED (+) cable to the positive (+) battery post
Tighten all connections securely and coat the installation
Please note that the directions require the components to be clean prior to connection. Clean does not mean slathered with grease. The clean connections are attached to each other. Clean connections are tightened. Then a grease is applied to overcoat the clean connections. The specified grease is not a specialty dielectric grease. It is the standard grease used as a general marine lubricant.
Dielectric grease is not a cleaner. Dielectric grease cannot restore corrode electrical connections. Dielectric grease is a very nice, very expensive, non-conductive grease with good heat resistance properties. Once you understand these principles, you can use dielectric grease in an appropriate manner to help maintain electrical connections in a marine environment.
posted 12-25-2009 10:57 AM ET (US)
Another example of engine manufacturer's advice regarding dielectric grease can be found in the service manual for a modern 225-HP outboard engine. In the chapter on installation and predelivery, in the section on outboard rigging, in the subsection on electrical harness connections, the following advice is given:
"Before installing electrical connectors, check that
Here Electrical Grease™ is assumed to be a dielectric grease. Note again that the grease is not applied to any of the electrical contacts or conductors themselves prior to connection. The grease is only applied to the seal.
A further mention of Electrical Grease™ is contained in the service instructions in the chapter on Maintenance in the section on spark plugs. The following advice is given:
"Apply Electrical Grease to the ribbed portion of
Note again that the grease is not applied to any of the electrical contacts or conductors themselves prior to connection. The grease is only applied to the seal.
A further mention of Electrical Grease™ is contained in the chapter on Electrical and Ignition in the section on connector servicing. The following advice is given in a subsection on Deutsch connectors:
"IMPORTANT: Electrical Grease is recommended.
"To disconnect the connector, press the latch and
"To connect the connector, confirm that the seal is
Note again that the grease is not applied to any of the electrical contacts or conductors themselves prior to connection. The grease is only applied to the seal. Later in this section instructions are given to add grease to the interior of certain connectors but in a manner to keep the grease away from the actual electrical contacts.
A further mention of Electrical Grease™ occurs later in this section in a subsection on AMP Super Seal connectors:
"IMPORTANT: Always use the appropriate
Note that use of electrical or dielectric grease is explicitly prohibited on these connectors.
posted 12-25-2009 11:04 AM ET (US)
In a prior discussion (see link below) a knowledgeable Mercury installer recounted instructions that dielectric grease was NOT to be applied to connectors in a Mercury engine electrical harness and rigging.
This can be considered another instance where use of dielectric grease on a connector was not recommended.
posted 12-25-2009 10:53 PM ET (US)
It should be noted in JimH's first post today (12/25) that in
the mention of the use of OMC Triple Guard grease the grease
is applied AFTER the battery connector is attached and
posted 12-26-2009 01:38 AM ET (US)
"Dielectric grease does not help the contacts in an electrical connector conduct electricity."
The above statement is true for "at the time of assembly/contact/connection" but once the contacts are exposed to air and moisture all bets are off.
Dielectric grease does not HINDER the contacts in an electrical connector conduct electricity, even slathering dielectric grease may yield an improvement.
Dielectric grease does help contacts in connections MAINTAIN contact by preventing oxidation and corrosion. It works by sealing out air and moisture. Even filing in tiny crevices where corrosion can occur. It's very much like spraying down engine connections with CRC but applied prior to assembly, it's more permanent, resistant to water and many chemicals/solvents. Water-resistant connectors are not vacuum sealed and still susceptible. A light coating on the pin side of the socket could be used if care is taken to remove any access from the silicone seals.
About 6 months ago these questions were presented to Dow Corning for clarification of DC4's intended electrical uses. Response was yes to all.
It really is not that expensive. You can apply it places marine is not recommended to be used. Consider it a good investment like using a good quality marine engine lubricant. The benchmark: Dow Corning 4 Insulating Compound, 5.3 oz. tube, with shipping less than $20 bucks. http://www.skygeek.com/dc4.html
posted 12-26-2009 10:36 AM ET (US)
It is really not a surprise that a manufacturer of a dielectric grease product would be enthusiastic about recommending places for it to be used. To make an analogy, if you buy a product like FELS NAPTHA soap you will find that it is recommended for cleaning just about everything known to man, and also as a remedy for a number of common human ailments.
When it comes to using dielectric grease on connectors in my outboard motor, I tend to be guided more by the recommendation of the manufacturer of the outboard motor than by the manufacturer of the dielectric grease.
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