Jan 28, 2019

Connectors and Connections

All Rights Reserved © 2014 Thomas W. Day

Anyone who has designed, repaired, or suffered the failure of any sort of modern electronic product knows that way too many product failures come from poorly designed, selected, or applied electrical connectors. My VW-based Winnebago Rialta was no exception, in fact it could be used to prove that rule. VW and Winnebago did some really dumb, cost-cutting, poorly thought-out amateur engineering moves with connectors on this van that contributed substantially to the vehicle and both companies’ poor reputations. In fact the connector applications alone would convince me that neither Volkswagen or Winnebago employs actual engineers.

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Under the best conditions, selecting the right connector for simple products isn’t an easy task. It’s hard enough to pick connectors for products that won't be exposed to the elements or high and low temperatures, drawing high (or extremely low) currents, and applications where either end users will abuse the connector or there is a lot of movement and vibration. Engineers have to balance all of the important qualities of the connector with price and delivery (which means instant availability for a JIT manufacturer). Too many consumer product engineers push the price decision to top priority and hope for the best with the rest. That’s an easy decision to make, if you have never done anything other than take a few college engineering classes and played a few video games. It’s a coward’s move if you are pretending to be a real engineer. The real world is a brutal place for electrical and mechanical connectors.

My winter of 2013-2014 was all about troubleshooting the electronics on the VW portion of my Winnebago Rialta. Based on the decisions I’ve seen from Volkswagen’s “engineers” and a few other similar product experiences, I have to assume too many modern product designers are kids with an experience database that does not extend beyond academia. Not one thing that I learned about from 30 years of engineering was applied to either the connector selection or application knowledge in our VW Eurovan. Like a lot of what I learned about management from years of working in mid-sized and large corporations, owning a Volkswagen is a lesson in “how not to” engineer and manufacture a product that contains electronic components. That is not an experience I will go through twice.

One of the first considerations an engineer has to make in connector selection is matching the materials to the application. If the connector will be exposed to heat, humidity or water, vibration, corrosive elements, and/or customer handling, the connector choice gets complicated. Hardware is where the expense lies in most modern electrical/electronic equipment, so the old “price, delivery, and quality; pick two” rule comes into play fast and brutally. If you’ve never had to consider those compromises, you’re building military-industrial crap that doesn’t have to work and nobody cares what it costs. The rest of us have to compromise something and often quality gets the axe because low cost rules everything in consumer products.

One of the jobs I had in my 30-year manufacturing career involved compensating for low-cost connectors. Long before anyone with engineering ability thought about the product, the marketing dweebs had set the price point and other gross product specs based on their many years of ignorance and arrogance. Once the price point was locked in, the design engineers specified low dollar connectors that often reacted poorly to pretty much every environmental component of the intended application. The connectors were contributing to a product failure rate that exceeded the design criteria. In one instance, when those products were returned for repair to my Tech Services department, the field failure rate for the same connectors dropped to zero. The difference was that our repair procedure for every returned product included cleaning all connectors with Caig Labratories’  Cramoline®  (now called DeOxit®). Since that treatment worked so well for the returned products, manufacturing started treating all of our new products' connectors with Caig's products on the assembly line and our connector problems vanished. Personally, I have used Caig Laboratories'  contact cleaner/protector/rejuvenator products for nearly 40 years as a post-design method of getting around non-ideal contact material selection. Spraying or scrubbing a little of those chemicals on to new and used connectors has prevented and resolved nearly a lifetime of connector problems. Likewise, locating and cleaning my Winnebago Rialta's plethora of crappy connectors with DeOxit® brought most of the vehicle's electronic systems back to life.

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A drip loop, the way wiring should be routed to prevent water from draining into the connector.

Unfortunately, the prime culprit in our vehicle's disability was the obsolete-and-completely-unobtainable Transmission Control Module (TCM). In the Eurovan's design, VW engineers demonstrated a complete lack of understanding the most basic concepts of connector and wiring harness design. Water leaking in through their poorly-gasketed windshield had followed the wiring harness into the connector. A common and necessary connector design tactic is to make sure the connector wiring has a “drip loop” to prevent water from following the wiring into the connector body. While it should be obvious that leaving some slack in the wiring to prevent connectors is critical, it isn't obvious to many rookie engineers/techs that water follows wiring back to the source unless there is an easier path. Worse, allowing a few inches of extra wire in a multi-wire harness costs a few pennies. Amateur engineers, like the kiddies from VW, cut the harness as short as possible to save those pennies, sacrificing any hope that the TCM would be safe from any water intrusion. Not only was our vehicle exposed to the elements but the wires drained so much water into the connector that two pins corroded completely away. The only available solution to this problem turned out to be hard-wiring around the damaged pins.

One of the other issues buyers need to be aware of in any product involving connectors is that many products will incorporate one-off connectors, which effectively become unrepairable when the OEM stops providing support. For example, Germany requires auto manufacturers to provide service parts for seven years after the last unit of a model rolls off of the assembly line. For our Eurovan/Winnebago, that support time limit ran out sometime in 2012. Unlike some companies, Volkswagen does exactly what it is required to do and not one tiny bit more, so if our electronic control components completely failed our only option was to find used parts. I have to suspect that Ducati owners will be experiencing that dilemma now that VW owns that label.

Finally, connectors should be secured so they do not shake themselves to pieces when the vehicle is in motion. Since the connector will usually be the heaviest section in a portion of a wiring harness, the connector will tend to move with the vehicle motion causing stress on the points where the wire is secured to the connector. Because of that, it is important that connectors are secured to something solid so they can't move and fatigue the wire and terminal connections.

The sad fact is that, even if you do all of the things I've described in this article, the weak link in any wiring harness is always the connectors and the point where the wiring joins to the connectors. Because of that, whenever I'm troubleshooting vehicle electrical problems, the place I always look first is the connectors involved. I haven't kept track, but I'd bet at least 50% of the problems I've resolved began and ended with connectors.

1 comment:

  1. Good article! On my BMW airhead, all of the electrical problems were no drip loop let alone a service loop and corroded connectors. I must’ve slowly replaced or repaired half of the wiring loom. The Ural just has cheap connectors that last just long enough for the first connection. Neither had enough electronics to produce major problems like your VW based motor home.

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