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Discussion Starter · #1 ·
So there is this Dodge van guy on another forum who started a thread on this topic on 07-01-2010, 09:31 PM

And he came back 4.5 years later to update it to share what he learned in the interim.

Bottom line is this for us with 15-20 year old vehicles: Our electrical contacts are oxidizing inside the plugs in our harnesses and the connections to our PCMs, etc.

For me personally, I have been diagnosing a "no canbus" no start situation or various sensor "open relay" trouble codes in my wife's 2000 Dodge Dakota 4x4 4.7L gasoline engine over the past year. And have gone through 5 defective replacement PCMs since.

I just sprayed some CRC contact cleaner into the three female plugs and on the bright brass shiny pins on the replacement PCM which I just received earlier this week, let them dry for a half hour -- and when put back together, the engine started immediately.

It was "no canbus" a half hour earlier.

Now I think that all along the problem or one of the problems has been oxidation on the three female plugs on the harnesses where they connect to the PCM and that I may owe an apology to the replacement PCM provider who graciously kept sending me new refurbished replacement PCMs under warranty.

I mean put a copper wire under the hood in your engine compartment and don't do anything with it for 20 years. Wouldn't it get black, green or some other form of oxidation on it which could make electrical connections intermittently fail or fail altogether?

I will order the:

1. mini Q-Tips

http://www.ebay.com/itm/Tamiya-Amer...efaultDomain_0&hash=item258b89a994&rmvSB=true

2. Caig DeOxit D5 spray

http://www.ebay.com/itm/Caig-Labs-D...efaultDomain_0&hash=item540ae3c3ea&rmvSB=true

3. Caig Gold contact conditioner

http://www.ebay.com/itm/CAIG-Labora...efaultDomain_0&hash=item3f2748f8ad&rmvSB=true

4. Caig Shield contact protector

http://www.ebay.com/itm/DeoxIT-Shie...efaultDomain_0&hash=item19ec71802a&rmvSB=true

All of which landyacht318 recommend in the following thread:

http://dodgeforum.com/forum/dodge-ram-van/251312-engine-shuts-off-bad-connector-to-pcm.html

and set about cleaning every electrical connection on the exterior on my wife's Dodge and on my 1995 Bronco and on my 2002 E350.

You may want to consider the same if you are chasing an electrical gremlin.

petrock on this forum said the following about vehicle electrical issues, which I now consider very wise:

"Mechanics look to the component. Electricians look to the wiring."


Guide to Caig products:

https://system.netsuite.com/core/me...wDAlJ1NDQH&vid=rfNKGgwDAmN1NHU2&cktime=131852
 

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1988 Dodge Dakota LWB RC 3.9V6 3 speed auto
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You say vs like it's one or the other.

Contact cleaner / enhancer on the contacts to improve the contacts, then the dielectric grease helps to keep oxygen from getting to the contacts so both. See, the dielectric grease is actually an insulator, but contact pressure is supposed to force it out from between the contacts, so that there's none THERE, but plenty AROUND.

That's almost like "Change the oil or the filter?" *grins*

RwP
 

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Discussion Starter · #3 ·
So after dropping my wife off downtown at 6 this morning I stopped by my much smarter friend Roger's to have more coffee on his porch. He said something that put it all in perspective for me, and it may help some of you too.

"Amps can't jump."

"Volts can jump."

"But only if the voltage is high enough."

That's why in a 12v gasoline engine vehicle, 12v can't jump the spark plug gap. A Tesla coil is needed to raise the voltage (from 25,000 to 80,000 volts dc depending on the ignition system) to get the volts to jump (i.e, arc. i.e., spark) that spark plug gap.

It is my understanding that those little PCM pinouts receive and transmit at 5 volts or less. Some maybe at millivolts. And it is not merely an "on-off" signal. It is an analog signal where the voltage may be (just guessing) increasing and decreasing millions of times a second from just a few millivolts up to a 5 volts.

"Millivolts to 5 volts can't jump."

So a direct contact from the copper pin to the copper receptical is required for a consistent signal to be received by or sent from the PCM.

That is probably why landyatch318 commented in his thread that not only did his engine start after he super cleaned and protected his PCM contacts, but his engine idled and ran more smoothly, maybe even saving some fuel. Because a PCM which is receiving or sending the entire range of millivolt to volt signal is controlling engine fueling and other processes that much better.
 

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Discussion Starter · #4 · (Edited)
RalphP: I wrote it that way to make people think of the proper use of dielectric grease.

Because my understanding is that "dielectric" grease is an insulator (just like a dielectric coupler which stops galvanized pipe from corroding copper pipe) meaning that it has the potential to prevent the passage of electricity from the male contact to the female contact in an automobile electrical connector.

I came across this thread about the use and non-use of dielectric grease in wet or corrosive environments such as in the adventure motorcycle world.

http://www.advrider.com/forums/showthread.php?t=533996&page=1

Check out post #9 on the first page. This is how it starts:

"Using Dielectric Grease on connectors.

A lot of people use dielectric grease on connectors. Some people mistakenly believe that dieletric grease is a conductor. In fact, it is just the opposite; it is an insulator. Dielectric grease is typically made of silicone grease.

As an insulator, dielectric grease is good for use on spark plug boots. This was one of the original applications on vehicles when the high-energy ignition systems came out. It can help insulate the connector and, in particular on a motorcycle where it can get wet, it waterproofs the spark plug boot. And, because it is silicone, it is fairly stable at high temperatures and won't affect the rubber and plastics.

So why would you put an insulator on a connector? The idea is that you use a thin layer. When you push the connector together the grease is pushed out of the way enough to get a connection and the surrounding grease then keeps out water and oxygen. The connector will be protected from the environment and less likely to corrode. Plus, the silicone is safe for the plastics and PVC insulation.

That sounds good, so far; so why not smear it on everything? Well there are a number of good reasons."

Finish reading the rest of that post, then take a look at the discussion of contact enhancers on page 2.
 

· The Anti-RUB
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That's why in a 12v gasoline engine vehicle, 12v can't jump the spark plug gap. A Tesla coil is needed to raise the voltage (from 25,000 to 80,000 volts dc depending on the ignition system)
Its not a tesla coil. A tesla coil in the engine bay would be awesome though. Lots of flashy lights jumping around inside.
The correct name is an ignition coil, which is a type of induction coil. It produces a couple thousand volts. I’m not sure if it goes as high as 25kVor 80kV though. I typically check for spark with a test light or an amp probe.


It is my understanding that those little PCM pinouts receive and transmit at 5 volts or less.
Most are 5V or less, but some are 12V too. It depends on the PCM.


Some maybe at millivolts. And it is not merely an "on-off" signal. It is an analog signal where the voltage may be (just guessing) increasing and decreasing millions of times a second from just a few millivolts up to a 5 volts.
Correct, kind of. It can be an analog or digital signal. It depends on the circuit and the component that circuit is driving or listening too. But your right in that some of them change voltage very very fast.


"Millivolts to 5 volts can't jump."
Well, yes it can actually. A few millivolts just can’t jump (a.k.a. arc) a relatively long distance like a spark plug gap. Maybe a few thousands of an inch or so. 5V could jump a little large distance.


So a direct contact from the copper pin to the copper receptical is required for a consistent signal to be received by or sent from the PCM.
Your on the right track here with figuring out what was going on with your PCM(s), but its not a problem with the voltage jumping/arcing. The problem is with resistance. Corrosion causes resistance in the circuit. Voltage is needed to overcome that resistance (as described in one of the RealFixesRealFast Voltage Drop videos I linked to in your other thread). But in overcoming that resistance some of the voltage is ‘consumed’. So you’ll have full voltage (whatever that may be) on one side of the resistance and considerably lower on the other. With the low voltage going across the the sensor circuits, a tiny amount of resistance can ‘consume’ that low voltage and render the circuit useless. That is the essence of voltage drop and Kirchhoff's Voltage Law.

As for contact cleaner vs dielectric grease, I agree with RalphP. Its not a one or the other type deal. They are best used together. However, I’ve never really been a fan of contact cleaner sprays. I prefer a very tiny set of files I picked up a long time ago somewhere in order to file off any corrosion I find on contacts and then apply dielectric grease to it to protect it from future corrosion. But to each their own.
 

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Discussion Starter · #6 · (Edited)
Micro Files

http://www.ebay.com/itm/171023369312?rmvSB=true

I am not disagreeing with the micro file approach, because I am the noobie here and have not used either the DeOxit products or a micro file (I ordered the DeOixt products on ebay and am waiting for them). However, to continue the contrasting perspectives, I thought I would post this from another thread:

landyatch318: "I would recommend not abrading the interior of the sockets with the files. Apply some DeOxit d5 or d100, let it work for an hour or two, then wet the micro q tips with more deoxit and clean out the oxidation. The first few precision swabs will get all torn up and turn black, but by the end they will come out clean and pink and the interiors will shine like oiled chrome.

Any filing will dig microscopic grooves and actually compromise conductivity long term. Also the connectors are tin coated copper, and the spring loaded arms, if filed, will have less spring tension to exert.

Stick with the DeoXit and precision swabs, IMO."
 

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I bet "landyatch318" sells Caig products or works for Caig. Trust me, you don't get a nice shiny connector back after its been corroded. Corrosion eats the metal and you have to either use something abrasive to get back to clean metal (just like grinding away rusted steel) or use a chemical converter (does not actually remove the rust, but converts it to something else like iron phosphate). Deoxit is basically overpriced denatured alcohol and naphtha (Zippo fluid) in a really expensive Qtip.

Deoxit has been hawked in computer repair circles for years for cleaning memory and expansion card contacts. People who spend hundreds of dollars on Monster cables swear by it.. Denatured alcohol is a fraction of the price and works just as well - if not better since it doesn't leave oily crap on the contacts.
 

· The Anti-RUB
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I agree with TazRango, I think “landyatch318” has some connection with the Craig products. The post sounds like it was written by someone in marketing.


Any filing will dig microscopic grooves and actually compromise conductivity long term.
Thats bogus. The only way filing would compromise conductivity is if you filed the pin down so far it was just a nub or you spread the contacts apart by sticking a large file into the contacts. The first can be fixed by applying a little common sense and the second could be fixed by bending the contacts back into place.


Also the connectors are tin coated copper, and the spring loaded arms, if filed, will have less spring tension to exert.
The "spring loaded arms" in most connectors have more travel then the fraction of a thousandth of an inch that would come off due to filing. And if it did file off more then that (which you would have to really try hard to do) you could just bend the spring loaded arm a little to make it come in contact with the pin again. Not a big deal.
 

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LOL wait a minute.. I just went and read through that thread.. He's not a salesman hes's just a fucking idiot!

In post 31 he tells you:

I would recommend not abrading the interior of the sockets with the files. Apply some DeOxit d5 or d100, let it work for an hour or two, then wet the micro q tips with more deoxit and clean out the oxidation. The first few precision swabs will get all torn up and turn black, but by the end they will come out clean and pink and the interiors will shine like oiled chrome.

Any filing will dig microscopic grooves and actually compromise conductivity long term. Also the connectors are tin coated copper, and the spring loaded arms, if filed, will have less spring tension to exert.
But in post 17 he says:

I have one of those fine diamond coated dremel bits which can fit inside of the sockets of my 14 way connector, and the smaller ones could fit in the 0 way connector.

Anyway I did the full physical oxidation removal with these tools and then a CRC flushing afterward, and the Deoxit still removed heaps of oxidation afterward. I was extremely surprised and impressed as the sockets went from rough and silvery to smooth and gleaming as polished and oiled chrome.
HE HIT THE FUCKING THINGS WITH A DREMEL DIAMOND BIT (a file that moves REALLY FAST!!) BEFORE HE USED THE DEOXIT! What a tool.

"Uhh DURRRR just put on this magnetic bracelet and it'll cure AIDS!"
 

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Discussion Starter · #11 ·
petrock and TazRango: Thanks guys. One thing is for sure, I don't have any association with Caig products. And I will report back what I find. It's hard for me to get in focus photos of things as small as the interior of a plug, but I will try even if I have to use a tripod and do manual focus.

And then we will compare before and after. And if before and after is not good enough, micro files will be in my future. In that latter regard, would you look at the ones that I posted (from ebay) and tell me if you recommend those or some others.

Thanks guys, I really appreciate the help. Quite frankly petrock's advice that mechanics look for the component and electricians look at the wiring was brilliant. And as you can see from the 5 PCMs I have gone through and the intermittent nature of the problem, I believe it is in the wiring, specifically the three PCM plugs.
 

· The Anti-RUB
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Those files are round, so it won’t work well for the flat socket connectors (where the male pins are flat). You’ll risk spreading the socket apart slightly. Flat files are better for that. However, the round files will work great for round socket connectors (where the mail pins are cylindrical). Good luck...
 
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