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For reference, touching the bare clean probes together read 0.8 ohms, or, essentially zero resistance.
Covering both probes with dielectric grease and then making contact would generally read 0.8~0.9 ohms. A negligible difference. (It shows 17.2 in the picture because they're not being pressed together).
I then tested the tail light assemblies I had previously cleaned and thoroughly covered in dielectric grease. Readings across connections were also in the 0.8~0.9 ohm range. I did have some trouble getting a consistent reading - I had not cleaned the oxidation from the non-contact areas. Digging in with the probes helped.
I also tested the resistance between the positive battery terminal and lug - also 0.8~0.9 ohms.
Just received an email from Permatex,
"Yes, Dielectric Grease is to be used on connectors and sockets alike. Its main purpose is to keep out corrosion, moisture and prevent voltage leakage. The grease is pushed out of the way physically by either the threads or pins of your application establishing a true metal to metal contact. The grease that inhabits all the surrounding extraordinarily small spaces where the electricity would attempt to arc will no longer have the ability to do so forcing all energy to the true metal to metal connection point(s)."
In summary, clean terminals and tight fitting mechanical connections is the #1 priority. Bathing everything in dielectric grease will maintain a good connection.
**I'm fairly certain that these ultra low readings on a cheap multi-meter are not accurate, but I think it does indicate that the dielectric grease is not impeding a good connection.
Multimeters measure resistance by passing a known amount of current through the leads and measuring the voltage. The amount of current generated by the multimeter is very small.
The dielectric grease will be more of a problem when you need to pass high current through it. Poor contact, such as greasy terminals, acts like a thin wire: you might see 0 ohms with a DMM, but it'll limit current. Even Permatex said that the key is reliance on the grease being pushed out to allow metal to metal contact. In practice, it doesn't all get pushed out.
You need to do a load test. Put the grease on your car's battery terminals and see if you get any issues.
Multimeters measure resistance by passing a known amount of current through the leads, and measuring the voltage across an internal resistor (which is also known). The amount of current generated by the multimeter is very small.
The dielectric grease will be more of a problem when you need to pass high current through it. The interface of two metal terminals with dielectric grease between them is like if they're connected with a thin wire. You might see 0 ohms with a DMM, but it's too thin to run your electronics. An actual wire would melt, but a poor contact will just limit current.
I've been thinking about this over the last couple days and agree that it doesn't necessarily confirm a 'good' connection under real loads.
I'll post an update once I get my car back together. If it doesn't start, I'll clean the di-electric grease off the battery terminals.
In the mean time, I'm going to keep reading into this - surely there are some technical papers out there somewhere.
At this point in the discussion I would like to refer to one of my first posts here where I say that if it isn't broken don't fix it...
For the connections with some corrosion I used some slightly abrasive cloth to just wipe the corrosion off...then find out why it has corroded now and not in the first year of the life of the car...probably a water leak of some sort that increases the humidity in the car under some conditions.
In my case, the car would start, but the temp and oil gauges would give odd readings sometimes, the voltage read low, and the car would crank a little slowly. Also, it was easy to kill the battery. So I thought I had a bad alternator. One day my friend is watching me wrench, I disconnect the battery first, and he's like "what's that stuff on your terminal?"
Last edited by FRporscheman; 02-24-2017 at 03:33 PM.
I cleaned a ground by the tail lights and now I have working brake lights again. I just noticed they were not working, no telling how long they have been out.
The trick is the very thin film, much like you would use on a CPU heat sink. You only want to take the place of air molecules, not metal. That said, I don't use any grease until after everything is connected.
These days, after cleaning and tightening electrical connections, I've taken to spraying them with Fluid Film. I have no long-term anecdotes to verify quality, but it is a very good non-permanent rust-prevention coating, and very easy to apply (spray it like WD40).
Back in the day, my starter would regularly corrode to the point where it couldn't crank the motor (presumably because it's on the bottom of the car and exposed to road salt). I coated every terminal with liquid electrical tape and it solved the problem.
02-21-2017, 07:17 PM
