Hello, fellow nerdz. I do a lot of harness repair and something just hit me - I see improper back probing every time, and I see it is all publications /videos/conferences that are held by pro auto techs. Most people back probe in a way that damages the weather seal of connectors. If you have never taken apart a connector, you will do something that seems logical but will end up damaging weather seals.

The improper way (but what SEEMS logical) is to back probe into the same hole the wire enters the weather seal. If you do this, you will get a connection, but you will puncture the weather seal and it will slowly tear itself all round as it heats and cools in the engine bay.

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The correct way to back probe is to go in between the weather seal and the connector housing.

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Sometimes when you insert your back probe, you feel the pin stick and get caught. Most techs force the pin inside when they feel this, and what you will feel is the pin will resist then proceed on as normal. NEVER do this. The reason it gets caught is that the pinhead has entered the crimp area. If you force it in, the pin will open the crimp area and proceed to go in. The unfortunate thing is this will feel very tight and you will get a connection but you have damaged your crimp.

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At times you insert the back probe, then feel like its floaty/puggy/ rubbery, and you get no connection. Reason for this is the pin is floating in the area above the crimp.

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If you want a good connection, you can do one of two things. Either remove the probe and just go opposite that point of entry (recommended) or push the probe forward (not recommended). If you choose to push the probe forward, you will get a connection at the pinhead itself like so....

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But this is dangerous - you may enter like this and spread that contact apart pretty easily.

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Finally, some car manufacturers use a very funny type of weather seal that becomes hard like contact cement (I'm looking at you Citroen, Peugeot, you bloody weasels). If you try and rape the connector you will destroy a lot of probes, and if you have a probe strong enough and loaded with viagra, what you will find is after it wins the entry, it will come out with the entire pinhead. In a case like this, save yourself the hassle and just pierce the wire.

I stand corrected kmech. Thanks. I have been dipping my probe tips in dielectric grease which I will continue to do.

fisher wrote on Jul 21^st, 2019 at 10:34pm:

I stand corrected kmech. Thanks. I have been dipping my probe tips in dielectric grease which I will continue to do.

Fisher, do you think that a bit of lubrication helps you get it in?

I absolutely hate and avoid back probing, two reasons
1. Potential for damage
2. An unreliable connection.

Your demonstration only supports my logic, good work by the way......

You will have seen my posts on break out leads that I make, the reason I make those is exactly for the reason that you rightly and generously point out.

Thank you

Agreed nice work!   [smiley=thumbsup.gif]

In saying I dislike back probing, I must quote an exception, itis a recent one.

A number of new BMWs have the engine control unit in a plastic box in the engine bay.

With the lid off the box one can back probe the terminals of the control units as the plugs are back windowed and one can freely see the unsealed connector terminals from the back side of the plug.

Not withstanding that, work that I'm currently doing on a F02 N57 with DDE7 has a series of 5 pin mcon connectors.

I have been using back probing at the DDE  control unit but also have ordered 5 pin male terminal connectors to enablt completion of several 5 pin mcon break out leads.




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Logic wrote on Jul 22^nd, 2019 at 5:05am:

You will have seen my posts on break out leads that I make, the reason I make those is exactly for the reason that you rightly and generously point out.

Please point me to the post or page of what you make.

K-Mech wrote on Jul 22^nd, 2019 at 7:13pm:

Logic wrote on Jul 22nd, 2019 at 5:05am: You will have seen my posts on break out leads that I make, the reason I make those is exactly for the reason that you rightly and generously point out. Please point me to the post or page of what you make.

Your wish is my command......

But only a touch on the number that I have made...so much so storage is an issue

https://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1556869362

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By the way sometimes I do not make break out leads, rather I make extension leads with a marked zone in the middle where I will use insulating piercing probes.

I do that so as to not waste construction components on a lead that I may not use that often.

In the event that I use it frequently I can complete it with 4mm banana jacks to a complete lead.


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By the way, whilst all of you Americans sleep I now have a friend in Kenya on the west pond rather than the right pond.

Logic wrote on Jul 22^nd, 2019 at 2:45am:

Fisher, do you think that a bit of lubrication helps you get it in?

;D

Andy_ wrote on Jul 24^th, 2019 at 7:39am:

Logic wrote on Jul 22nd, 2019 at 2:45am: Fisher, do you think that a bit of lubrication helps you get it in? ;D

We need a face palm simile. I wasn't gonna go here.  :o

I wish I had a picture of the PCM breakout box for Maserati. It is probably 2' wide. Maserati definitely took Picoscope diagnostics seriously.

James Kelly wrote on Jul 24^th, 2019 at 5:20pm:

I wish I had a picture of the PCM breakout box for Maserati. It is probably 2' wide. Maserati definitely took Picoscope diagnostics seriously.

  ????  Is this it?

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Logic wrote on Jul 24^th, 2019 at 6:44pm:

????  Is this it?

That's the one! I'd love to have something like that for Land Rover (Bosch PCM).

Spence wrote on Jul 24^th, 2019 at 9:08am:

face palm

🤦

;D

Steven McGrew wrote on Jul 27^th, 2019 at 12:30pm:

Spence wrote on Jul 24th, 2019 at 9:08am: face palm 🤦 ;D

I could use one to respond to your post!   [smiley=laughing2.gif]

James Kelly wrote on Jul 27^th, 2019 at 11:24am:

Logic wrote on Jul 24th, 2019 at 6:44pm:   ????  Is this it? That's the one! I'd love to have something like that for Land Rover (Bosch PCM).

Interesting I have been doing a lot of work on break out box design, I have one design based on units of 26 pins which is interesting.

There are some issues with break out boxes and one of them is bulk.

Can you imagine tring to drive a car with the Maserati break out box.

Another thought that I have is to simply make extension leads.  Even there one can have options, straight extension, Y extension or V extension.

One could use a factory header connection on the V or Y , then one could either connect channels into each pin or bake probe the denuded connector housing.

That results in a very cheap , compact and effective break out system.

Logic wrote on Jul 27^th, 2019 at 2:41pm:

James Kelly wrote on Jul 27th, 2019 at 11:24am: Logic wrote on Jul 24th, 2019 at 6:44pm:   ????  Is this it? That's the one! I'd love to have something like that for Land Rover (Bosch PCM). Interesting I have been doing a lot of work on break out box design, I have one design based on units of 26 pins which is interesting. There are some issues with break out boxes and one of them is bulk. Can you imagine tring to drive a car with the Maserati break out box. Another thought that I have is to simply make extension leads.  Even there one can have options, straight extension, Y extension or V extension. One could use a factory header connection on the V or Y , then one could either connect channels into each pin or bake probe the denuded connector housing. That results in a very cheap , compact and effective break out system.

I have seen pictures of Ian's breakout leads. They are second to none!

Logic wrote on Jul 27^th, 2019 at 2:41pm:

Can you imagine tring to drive a car with the Maserati break out box.

TBH, I can't even remember where the PCM is on most of the Maseratis. It wouldn't be too bad in a newer Land Rover as the PCM is right next to the brake booster and is very accessible. The cables for the Maserati breakout box look long enough to reach inside the car.

K-Mech wrote on Jul 21^st, 2019 at 9:59pm:

Hello, fellow nerdz. I do a lot of harness repair and something just hit me - I see improper back probing every time, and I see it is all publications /videos/conferences that are held by pro auto techs. Most people back probe in a way that damages the weather seal of connectors. If you have never taken apart a connector, you will do something that seems logical but will end up damaging weather seals.

Thank you K-Mech! I am one of the ones who was doing this incorrectly, but not anymore! ;)