Electrical Connector and Terminal Service
Electrical Connector and Terminal Service
One of the most rapidly growing and demanding area of motor vehicle service is the realm of electrical diagnosis, ranging from basic electrical circuits through advanced electronics. With most systems having integrated electronics, there is no longer "room" in the trade for those whose claim is to only demonstrate an interest and capability of providing service on only mechanical systems.
Now, if you are already consider yourself to be an expert at everything, stop here and read no further. However, this lengthy "Marticle" (Martin's Article) is designed to provide and share some insight into servicing electrical connections and wiring terminations as used in the GM vehicle realm, as repaired in GM dealerships.
However, it may just contain a few "tidbits" of useful information for others who may work in an environment where information, tooling and support may be lacking. When servicing modern technology electrical connections, it can be an extreme challenge resulting in frustration and accidental component damage if we are not properly equipped and have sufficient resources.
So, my long-time experience as a GM technician and trainer is founded on having nearly all of the tools and equipment required, in order to perform diagnostic testing and repairs to a prescribed standard. However, I also lived in the "real world" service bay environment for many of my past 50 years in this trade. I sometimes worked in less than optimal circumstances, where an adeptness for creativity was often necessary, to get the job done quickly and to achieve industry standards or better.
The all encompassing diagnosis and repair speciality that falls under the electrical category, frequently requires inspection and replacement of electrical connectors and terminations, of seemingly ever-diminishing physical size that may be located in nearly inaccessible spaces and with wiring harnesses that are too short to repair comfortably.
Typically, from the 1980s for several years, many of us dealt with servicing of electrical connectors and terminals that were significantly larger in size than their current counterparts, such as shown in Figure 1 and Figure 2 views of an older Packard Electrical Division (PED) connector as used on GM vehicles. This connector has a front Terminal Positive Assurance (TPA) lock, rear TPA with conductor separator and retention, sealed terminals and the Connector Positive Assurance (CPA) lock that retains the connector on the component. These were/are serviced far more easily than many of the more complex connectors used in current applications, given the overall size difference and ease of access to the terminals.
With advanced molding techniques, a connector that might once have been a single component, perhaps with a seal and a Connector Positive Assurance (CPA) lock, may now be assembled from four or five separate pieces with a main connector body, an insert or carrier, along with multiple Terminal Positive Assurance and Connector Positive Assurance locks. Careful handling and re-installation of such pieces is critical to proper repairs, due to tight manufacturing tolerances of the mating components. They can be damaged easily.
Whether learning in the automotive field is accomplished such as via apprenticeship in Canada or similar training in USA is available, the major learning category that encompasses electrical and electronics, generally still appears to play only small part in exposing technicians to connector and terminal service procedures. Given the wide array of component manufacturers that are suppliers to vehicle manufacturers, it seems that there is a more generalized approach to describe and perform some basic electrical termination services.
In other words, technicians typically learn from experience on the job, unless they work in a dealership environment, where related training may be available during or beyond apprenticeship.
Discounting years …, my time spent as a technician since was with a General Motors dealership from … and subsequently as a trainer in the same system. So, I will focus on service of electrical connectors utilized by GM. Since many manufacturers share the same suppliers, some methods and tools identified here may be the same, transferrable, similar or differ amongst various vehicle manufacturers. Many use common components such as modules, components and conductor termination systems, from a select group of suppliers.
The challenge that many technicians may face daily, is performing repairs and replacements to connectors and wiring terminations. Without detailed service information, it can be easy to damage fragile connectors that may be considered relative "unobtainium", unless significant research yields available replacement components.
It is pretty safe to say that the terminations in Figure 3, were typically representative of electrical terminals available and in widely in use well into the 1970s and that are still available from parts "houses" today.
However, it is fair to state that these terminals, while robust, did leave some concern for the esthsetic quality of a professional repair. With some work the basic terminals could often be used and the final repair tidied to resemble an original connection or at least bypass a burned connector body that was not readily available. Today, close enough is simply not good enough, with fit and security of connections being absolutely critical for operation! So, we have come a long way since those times, but servicing of connectors and terminals has become increasingly more challenging.
For many years, General Motors dealerships throughout North America have utilized a terminal repair system Figure 4 that was both complex and incredibly expensive. It was originally housed in a "fishing tackle" sized box with a few red terminal compartment trays, crimpers, soldering tools and not much more. As connections grew more complex, the system was expanded several times until the current 30 tray storage system was created.
It was designed so that dealership technicians could readily locate service replacement terminals efficiently. With this system, a training course was offered and incremental changes in procedures and tooling added over several years.
However, without any training, some technicians were never able to maximize their efficiency in using the tray system and supporting information and tools.
Major incremental updates to the storage system, dictated that in order to organize the trays and components to the most current version, specific steps had to be followed. It was not possible to go from "A - Z" without completing several steps in between in sequence. Many dealerships did not complete the updates and uninformed technicians ultimately found the system unusable. With the current continued practice of globalization and downsizing of electrical terminations, the terminal system still has a place as an option for an alternate method of repair, such as in situations where a small harness replacement might be the preferred method of service, but inhibited by a back ordered harness.
General Motors current direction towards repairs is known as the "Global Wiring Repair Strategy" and is supported by the following actions:
- Minor electrical harnesses such as those in steering columns, seats and doors should be serviced by harness replacement. - Major harnesses are generally repairable. How this may be accomplished can depend upon a number of factors. Service information may list options for connector and terminal replacement, terminated lead, or "pigtails" for smaller connectors with 8 cavities or less (connector with terminated leads), depending on the model year of the vehicle and system as listed in SI. Increasingly, it will be noted that service replacement terminals along with their location in the storage system and associated tooling, have been removed from SI to support the use of terminated leads.
However, the option to replace a terminal instead of using a terminated lead as above may be a desirable alternative repair method, depending upon several factors:
- Availability of the requisite terminated lead and timeline for delivery - The same connector may have been previously serviced with terminal replacement for prior model year vehicles of the same component build. - The shop J-38125 terminal kit is well-organized and replacement terminals are in stock. - The associated tools to effect a professional terminal replacement are present. - The technician has the expertise to utilize the information system, tools and components to effect a proper repair in a timely manner.
It is typical for technicians to wonder why such a complex array of wiring and connector terminations might be deemed necessary. For a low volume vehicle manufacturer this may be kept to a minimum. However, for larger volume manufacturers such as General Motors, the sheer volume of components from the suppliers, dictates that vehicle harnesses be assembled with specific terminations, as designed and assigned by the component supplier.
The terminal tray storage system itself with 30 trays of individual 30 compartments and uniquely labelled, is indicative of the various suppliers and harness manufacturers, so there is no provision for GM to keep electrical termination styles simple at the vehicle manufacturing level. Component manufacturers dictate the connection system that is required.
For those technicians performing electrical termination repairs at GM dealerships in Canada, an updated terminals and connection service course was created to ensure that the technicians have the most current training and expertise to use SI, the available components, tools and service procedures efficiently. This is a hands-on course and is instructed in both GM Product Service Training and in GM ASEP, with a slight variation in component harnesses used at the bench for identification purposes. The course does provide all of the relevant information so that technicians can perform electrical termination repairs to the required standards efficiently.
For technicians working in general repair facilities, without any training or purchase of preferred special tooling and ready access to service replacement components, it can be a little more challenging to perform the same repair as quickly, since the technician may only have SI available, which is only one piece of the "puzzle".
However, the reality of the situation is no different, for those technicians in GM dealerships who also lack the training, expertise and awareness of how many processes, tools and components factor into completion of performing high quality terminal and connector repairs.
While one dealership might maintain all of the tooling and terminal storage system in proper order, it has been said that another may have the whole collection residing in a wheelbarrow for portability. This creates a very different need for technicians to perform the repair that will best fit the scenario.
While a well-organized system may support a terminal replacement as an accepted alternative to the GM global wiring repair strategy, a technician working with the "wheelbarrow" scenario, is likely much wiser to follow the global wiring repair strategy! Unfortunately, this does negate the possibility of the repair being completed sooner, depending on component availability.
While there are still many large wiring terminations and connectors on motor vehicles, many of the sub-systems and notably those that are networked, have been of diminishing size in recent years. An example is that with the more recent adoption of Ethernet, some of the connections have been reduced in size from 0.64 mm terminal size that has been the mainstay of module connections for some years, to 0.5mm Mini-50 or Nano terminals with up to 5 amp ratings.
The challenge for technicians performing diagnosis and repairs, is servicing these ever shrinking connectors with tools that are effective, while not damaging to what appear to be quite complex connector components manufactured from what generally feel like rather fragile materials.
What follows below, will focus on some common repair strategies and tools for connectors widely used in GM vehicles for network connections to various modules such as Body Control Modules (BCMs) and Infotainment system components such as radio module Ethernet, Telematics (Onstar) and similar connections, which may be as small as 0.5 mm.
Along the way, some obstacles to service procedures using supplied terminated leads may be encountered. One such issue is creation of terminated leads with the largest possible conductor that the terminal is capable of supporting.
While the terminal to terminal connectivity may be correct, the connector body that houses the terminals may not have sufficient space in the connector cavities to accommodate the insulation material of a larger diameter conductor, than the original wire. As such, there may be one or two options to explore when encountering these situations as shown in Figure 5.
Now, while I am fortunate to have access to all of the prescribed vehicle manufacturer service tools, I am also well aware that technicians including myself, may have to be creative and adopt alternate methods and tools to complete a repair, when the preferred tools are unavailable, or perhaps priced unreasonably that purchasing a tool for a one time use may be deemed impractical.
One specific area where there are definitely standards to be maintained without deviation, is in Supplemental Inflatable Restraint systems, aka "Air Bags" and related components. Terminal crimping is limited to butt splicing of harness side terminations and connectors with gold plated terminated leads and no repair or replacement of component side harness or connectors. Exceptions may be elimination of an inline harness connector body with a specific repair routine. Repairs to these systems are not the focus of this post.
One of the most significant challenges for the servicing technician, is accurate identification of a connector and terminations when requiring replacement. While service information may provide some insight, the technician may have to do some research and close-up inspection in order to identify a specific connector body by its manufacturer's name in full, abbreviation or one of multiple logos/symbols used to represent the organization.
In some instances, the manufacturer identification might also be located on the Terminal Positive Assurance (TPA) lock as shown in Figure 6.
However, locating the relevant symbol on a miniaturized connector body can be an extreme challenge, at least for these old eyes, without a magnifier visor or similar as in Figure 7. Figure 8 shows some of these as in use on GM products.
We must also take into account that while servicing connections at the bench or in this post may appear straightforward, this technician is painfully aware from experience of working with connectors in hard to access locations, where there insufficient conductor length to accommodate ease of access. It is however, important to make the work space as comfortable as possible, with sufficient clearance to use the associated service tools effectively.
We will first take a look at the A11 radio X6 connector as used on … GMC Terrain at the Harmon radio module for Ethernet connections to the Telematics and Audio Amplifier circuits. The connector body is approximately 3/4" in length and 3/8" width when closed and serviced only with a replacement connector and/or terminated leads as necessary. It is readily accessible by lowering the radio in the mounting bracket, or complete removal after disconnection of all connectors. Figure 8 inset shows the general construction of the 12 way connector body, which opens on each side to reveal the locking lances that retain the terminals.
Close up 10X magnified inspection of the X6 connector body in Figure 9, reveals Molex as the manufacturer.
The connector might be described as a two row "clam shell" design, with 12 terminals in two rows as in Figure 10. Terminals 1 - 4 are on one side and 5 - 12 on the opposite side. As is often the case, close inspection on the reverse side of the connector body will reveal these terminal number locations molded into the body material at the ends of each row. The release tool for the locking lance is identified in the call out. However, other options to gently lift the lance to allow terminal removal will work as well, or better when used carefully.
From personal experience, the steep rake angle of the J…A release tool serves well when a front TPA is staged and used as a guide for the tool entry, but less so in the above application.
The J… in Figure 11 has a lesser angle chisel point and fits under the end of the locking lance to lift the lance more easily. Care is required to not force locking lances to extreme positions, so some finesse will preserve the integrity of the lance.
Researching the connector from the link in the associated SI wiring schematic, provides all relevant information.
The harness type is identified as "Instrument Panel"
The OEM and Service Connector are the same part number: … - Often, service replacement components carry a different part number. Note: If researching connector supplier web sites, using the OEM part number is usual practice.
Description: 12-Way F (Female) Mini 50 Series (BK) - Black
So, we can now be sure that we have identified the correct connector and viewing the associated terminal pin assignments would verify this to be accurate.
Reference materials such as the chart in Figure 12, may be useful towards identification of a connector manufacturer.
Information is listed in table format as in Figure 13, identifying available parts for service and any associated tools or alternates as may be the situation for some terminations. If for example a terminal was available for service replacement, the service terminal part number, tray and crimper "nests" for the core and insulation would be listed.
However, there are and will be no parts and tools availability for terminal crimping of Mini 50 or 0.5 mm terminals
Connector terminals are identified by type using Roman Numerals, typically I II III and IV. "N/A" identifies that there are no approved terminations or tools other than the listed terminated lead as shown in Figure 13.
So, now we have everything necessary to perform a professional repair to the Ethernet pair wiring at the A11 radio X6 12-Way connector.
The reality of performing high quality connector and wiring termination repairs, falls squarely onto the shoulders of the service technician, to interpret and understand the requirements, be fully aware of related information, component and OEM spec or alternate quality tool availability as necessary. No matter, the quality of the finished repair will depend on the expertise of the technician while being extremely careful not to damage small connectors and terminals during the process.
Another Ethernet connector and service tools is shown in Figure 14.
Now, to the diagnostic aspect of working with a terminal that is suspected of a poor pin fit. Many modules to date on GM vehicles, have utilized 0.64 mm terminal pins. Terminals may be round or square in cross section and the J-35616-64B test probe is a square section probe tip that is designed to connect to both round and square cross section terminals for diagnostics and also inspection for terminal pin tension using the "drag" test.
While my own test kit is maintained in good condition and any damaged probe tips replaced when necessary, it is highly likely that rough use in a high volume repair shop may result in the probe tips becoming bent during heavy use. For this reason, a better alternative to inserting a bent probe into a terminal which in the process may spread and lose tension, is to consider using a new terminal of the correct size as shown in Figure 15. Again, I do understand that in the real world a technician may not have ready access to replacement terminals. However, those of us who are detail oriented do recognize such possibilities and are prepared, by having spare terminals in our tool kits.
An aside note, the EL-35616-58 test probe as shown in Figure 16 is used for connection to an testing Mini 50 terminals and appears to have probe tips manufactured from a more robust metal such as spring steel and despite the significantly smaller size, they do seem to stand up well in service and are more resistant to distortion.
Let's take a look at Body Control Module (BCM) connection service. For many years since the mid-2000 timeline, GM has widely used Japan Solderless Terminal (JST) produced 7 connector BCMs in various forms. For those interested, here is a link to the company web site. jst.com/home4.html
Figure 17 shows a JST BCM having 7 possible connector cavities with similarly-sized connectors, each with unique indexing to the module.
These connectors can be particularly challenging for some technicians to make repairs such as installation of replacement terminals due to extremely limited space around the terminal and insulation in the connection cavity. The terminals are tang-less design, retained in the connector body with locking lances that must be gently moved horizontally in order to release the terminal. Crimping of replacement terminals requires the use of proper tools and techniques so that the resulting crimp is properly secures the conductor core and insulation, without any distortion that prevents entry of the finished termination into the connector cavity.
Since GM uses TXL wire, the insulation is sized to fit the cavity and if the wire needs to be replaced, only TXL conductor will fit. So, in a situation where the wire is damaged or requires extension, in the absence of having TXL wire on hand or readily available, it may be necessary to trim a piece of TXL wire from the harness and butt splice a length of generally sourced replacement conductor in between, since the larger insulation diameter will not fit into the connector cavity.
Figure 18 shows two of the BCM connectors showing the unique indexing features that prevent plugging the connector into the incorrect BCM connector cavity.
It is important to understand the construction of the connector and how terminals are retained. Tang-less terminals are retained in the connector using molded locking lances that require extremely careful use of specified release tools or suitable equivalent.
Get this step wrong and the fragile tip of the locking lance will round over and rapidly become extremely challenging to release the terminal from the cavity! The original prescribed tool does not work well and a better alternative has been identified. Regardless, technicians generally find this particular connector challenging to service, since it is hard to see the locking lance. So, appropriate insertion of the release tool at the correct angle and depth is critical to release of the terminal and preserving the locking lance in good condition.
The JST BCM connector in Figure 19 is of a "hybrid" design, able to accommodate terminals of two sizes.
A close-up view of the connector cavities in Figure 20 shows the locking lance. Viewing the larger terminal and release tool entry canals, provides an enhanced perspective of the locking lance mechanism.
Before discussing the service procedure, some nomenclature of the associated component parts of the connection are in order, along with an understanding of whether removal or "staging" of a piece is required for terminal removal and installation.
The white plastic Terminal Positive Assurance (TPA) lock in Figure 21 requires staging (re-positioning), by carefully lifting with a pocket screwdriver until a single "click" is heard. Without this step, the terminals cannot be released, regardless of moving the locking lance.
Unlike some connector bodies, the white TPA in the JST connector cannot be removed from the connector body until all of the terminals have been removed.
To clarify why, Figure 22 shows a disassembled view of another JST BCM connector body with the TPA removed.
So, let's prepare to install a replacement terminal, by trimming the insulation back 5mm as shown in Figure 23. Make sure to use a wire stripping tool suitable to the wiring gauge, no side cutters or teeth. All strands must be maintained undamaged in order to complete a mechanically sound finished crimped termination.
The next step is to position a replacement terminal into the appropriate nest of the specified or suitable alternate crimping tool as shown in Figure 24.
Once the terminal is captured squarely in the crimper nest, insert the prepared wire to position the core and insulation in the correct position in the terminal, ready for crimping as shown in Figure 25. Note: It may be necessary to gently form the insulation crimp "wings" of the terminal to better conform to the jaws of the crimper nest, so that the crimp will fold around the insulation properly.
The completed crimped termination should be straight and capture the core and insulation as in Figure 26. Hand crimping even with the prescribed tools, can result in some small "tweaking" of the finished crimp to "finesse" the finished dimensions to allow the terminal to fit into the connector cavity.
The finished termination should enter the connector cavity easily, while holding only the conductor. If the terminal is too tight due to not being straight, or the conductor insulation crimp causes binding, adjust as needed.
With the terminal inserted into the connector cavity and the TPA locked in place, there should be a slight "end play" when gently moving the conductor. If the terminal is jammed into the connector, with no room to move, terminal fretting will result.
Here is a short video clip of the finished terminal installed into the connector body
GM SI now incorporates some video clips of electrical connector servicing procedures and tools. Shown in Figure 27 (courtesy GM SI), is the "better" option terminal release tool than the originally specified tool. However, note that these are now MP4 videos and are not able to be viewed with Windows 7 64 bit PCs using Internet Explorer 11, which is the preferred browser for SI. However, Google Chrome can be used to view the video clips, but does not support other GM plug-in requirements at this time.
Figure 28 shows a comparison between the original specified release tool J-38125-12A … and the J… that serves the purpose better.
Notable is that the J… also serves well to lift the locking lance on the Ethernet connector body discussed earlier than the J…A tool
Note: Do not use the release tool to stage the TPA as the tips can be easily damaged, rendering the release tool useless for its intended purpose and also resulting in damage to the connector body and/or TPA.
These release tools are available through Bosch Service Solutions by single part number or packaged in alternate options such as the EL… Terminal Removal Test Kit in Figure 29 that contains the most common release tools in current use, at an affordable alternative cost to the significantly more expensive J… kit box in Figure 30 The larger kit contains all previously used terminal release tools, which we purchased at a whopping $550 CAD just a few years ago! Checking the 2018 price in US$, in Figure 31, the price we paid, now appears to have been a relative "bargain"!
Now, let's take a look at servicing of a more recently used BCM connector manufactured by Tyco Connectivity, that is currently in use in the … GMC Terrain and sister model vehicles.
The overall size of the connector shown in Figure 32 is slightly smaller than the JST connector described above and while connector service procedure is very similar, the process is much more easily manageable than for the JST connector.
The locking lance in the this Tyco Electronics connector body must be moved vertically to release the terminal, in comparison to a more awkward horizontal movement in the JST. Overall, there is far more room for release tool access in the entry canal. Sitting at my desk one evening with a TE BCM connector in hand, I discovered that a wooden toothpick could be used to quickly release the terminal from the connector, with no risk of damage to the locking lance or connector body as shown in this short video.
Additionally, the most current version of the J-38125 Terminal Repair Kit Instruction Manual (J…H) can be purchased in paper version and found online through various sources. (Download at your own risk) While the manual has not been updated in some years, there are nice photographic representations of many connectors, tools and servicing, along with supporting information related to terminal service.
Connector and terminal servicing is also supported in GM SI. E.G. Here is the file path for a 2019 GMC Terrain - using a document keyword search "connector" will lead to multiple related documents in "Wiring Systems and Power Management" Document ID # 2413364 provides information about the various connectors. While this is only black and white, there is useful information in the document to support identification and servicing.
Hi Marty: Very well done. Thanks for sharing. Guido
Another great article of valuable information you just shared Martin! Over my 40 plus year career I’ve often struggled and become frustrated with terminal releases thinking “a human shouldn’t be dumber than a connector, right?” Reading your details on this topic helps shed more light on just how complicated those seeming simple terminals and connectors actually are. I can recall that 1st “tackle…
Thanks David. Dealing with connectors and terminals can definitely be a challenging experience at times, even when informed and properly tooled! Even with the information, some connectors can be very stubborn to deal with, especially the first time around. Learning on the job without any training can easily result in damage on the new breed of connectors. The material that some of the connectors…
Hi Martin! I have always enjoyed your presentations. I do a fair amount of terminal and connector replacements for collision centers, repairables and shops whom have practiced bad practices in proper probing. I find it challenging to service the new connectors as you have stated due to accessibility and their relatively small configuration. I have to use a lot of lighting and magnifying glasses…
Thanks Bob! I've made a note to self, to capture some clips when I'm struggling with new connectors! Thanks for the insight. For the most part, identifying the connector by manufacturer can often be a challenge, especially for manufacturers such as Sumitomo, whose symbol would fit on the head of a pin! Adding to the frustration, is when a connector body in NA in colour (any natural variation of…
Very well done Martin! I personally find this kit very effective for multiple car lines. steelmantools.com/universal-term…
Thanks Bill. Our main campus tool crib has those on the shelves too. There is more than one way to get the job done just as professionally for sure!
Million Thanks. Very Good Info!. Wehre is the Big Green Thumb UP? Can I save the Article in my files for later "digestion" ?
Hi Alvaro, Click in the bookmark button in his post for quick reference.
Thanks Alvaro. It is simply about giving back and sharing so that others may have an opportunity to elevate their skills in the challenging environment we work in.
If this is too close to advertising, take it down. Posting because it lists the sometimes difficult-to-find GM part numbers for spools of TXL wire.
Hi Mike. I personally believe that fair representation for the purpose of education is absolutely reasonable. It is important for those wanting to perform top notch repairs that the entire "XL" range of conductors is readily available and where it can be obtained easily. Our student work guides also list TXL on 50' rolls for handy reference.
Thanks for posting that Michael. I'm printing it out at work come Monday for next time we need to order wire for repairs.
You Sir are one class act. I can't imagine how much time it took to put that together. I've never regretted a spending any time reading your "Marticles";-) Now I can print this out and show my Boss and say, "This is what you don't realize that I have to know and deal with every day". I had to learn this all the hard way, by reading page after page of service info.
Aw shucks Jon. I'm blushing. LOL. Seriously though, you said what many of us have had to experience during our time wrenching, "I had to learn this all the hard way, by reading page after page of service info." So, if a little assistance on my part is able to lessen the frustration for others, the time spent is more than worth it.
Great article Martin. Thanks for taking the time and effort. I always learn from your great posts!
Thanks John. Knowing that others appreciate the info makes the time and effort worht it!
Martin, I'll join the chorus and say thank you for such important information. Of course you in this thread have been contributing such for decades, I thank you. The respondents are all so familiar because they are all long time important contributors. Who for years have contributed to raising the professionalism of this too often maligned trade. It makes me even prouder to be a member of this…
Thanks Tom. You words are much appreciated. Everyone who spends a little time giving back here and in other forums, can make the automotive field a better place for all who want to learn and improve our knowledge and skills. Often times, I tend pick and focus on some of the seemingly more mundane and notably overlooked fundamental aspects of automotive service. The reason is simply because these…
Not sure if you mentioned it, but the EL-35616-58 IS NOT 0.5mm! It is a 0.4mm round probe. The 0.5mm Mini-50 or Nano terminals used in GM vehicles are actually 0.4mm thick and .05mm wide.
Hi Joe. You are quite correct, the test probe is round in cross-section to match the blade thickness. In training, we do spend time measuring both the male terminals and the probe dimensions. It becomes quite clear and more fully comprehended under the close scrutiny of a micrometer, being able to identify various terminal series sizes, retention methods (tanged and tang less) and indexing…