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A Rogues Gallery

of 

Aging Connectivity Elements

Oftentimes technical discussions refer to devices and concepts as if everyone had the same background and experiences with the subject matter.  In order to be more clear as to where “Intermittency” or “Glitching” comes from as it relates to electromechanical aging, we put together a few pictures of one of the worst cases we have seen.  

When we refer to “connectivity elements” we are referring to those electronic devices that simply transport a signal of interest from one component to another.  Included in this category are wiring, solder joints, the copper runs on a PC board, connectors, relays, circuit breakers, power busses, etc.  Basically, any hardware type of element that does not modify the signal as its primary design function is included in this class.  We can also include the “connectivity elements” that form a connecting function for active components, such as the external and internal leads of IC chips and transistors, as well as the wire wrapped around a core to form an inductor or relay coil.  Basically then, for test purposes, any element that will allow the passage of a current. 

These particular pictures all came from an automobile that had left a series of owners inadvertently stranded. Several times this vehicle has had to be towed off of the freeway, and each time it was taken to a professional garage for repairs where the answer has consistently been “We cannot find anything wrong with it”.  This is a typical “No Fault Found”. 

 The actual problem the owners have faced is that it simply stops running when it feels like it.  No warning symptoms and no time to even pull to an outside lane.  While not as dangerous as an aircraft engine problem, there is still an element of danger when such breakdowns could trigger a pile up on a freeway during the early morning commute.  We wouldn’t want to risk driving it anywhere.

 When we were asked to help, the car would not even start any longer.  However, most times the car would restart by the morning after being towed home or to the garage.

 In tracing down the primary cause this particular time, no fuel pressure, we soon located a corroded terminal and wire socket on the main fuel boost pump.  As soon as fuel pressure was restored, the car again started.  Being a little cautious about such an easy fix after so many other professional mechanics had failed, we started doing a little exploratory visual inspection of the rest of the wiring. 

 The first relay we pulled down from under the dash showed signs of massive over-heating on one of the connector pins as well as the insulation to the attached wire was burnt off for about a quarter inch.  (See the attached picture).  In an aircraft, or elsewhere, this is pretty typical of what we like to call I2R (“I squared R heating”),  the Ohms Law formula for wattage.

 You take just a few amps, and judging by the gauge of this wire (see the red wire) it can take a few amps, so lets say 10, and run it across a 1 ohm resistance between the socket pin and the relay pin, and you get 10*10*1 ohm or 100 watts of heating on a very small heat dissipation surface area.  Things are going to burn and smoke.  The metal part of the connector pin, as you can see, has been burnt black.

 While testing this or a similar device for ohmic value with a precision meter, you might be able to measure the hypothetical 1ohm of resistance, but more than likely, even if you do, you might not immediately recognize such a low value of resistance as a defect.  It becomes a major defect in operation however because of the large amount of current being carried.  However, judging by the looks of this burnt connector, it is probably highly intermittent also, so testing for “glitches” may be the better testing method.  We checked a couple of other relays under that same side of the dash and they looked satisfactory. 

We then went to the other side of the vehicle and obtained access into the cars computer area.  The car was running at the time, and when we touched the next relay, the car immediately stopped running.  A couple of retries confirmed that we had a second problem causing the auto to shut off inadvertently.  (The rest of the attached pictures are of this relay.)  Unlike the relay with the burning socket, this socket and wire bundle looked perfectly good.  As you can see in the picture, this relay also had a plastic case that stopped us from visually inspecting inside of it.  Suspecting to find some worn-out relay contacts, we pried the cover off.  As you can see there are two relays and a couple of diodes and resistors attached to one side of the mounting printed circuit board.  We got out our magnifying goggles and lights and inspected the solder side of the board. 

We counted 24 component leads coming from the topside and 19 of these had cracked or worn out solder connections.  Since as you can see, in trying to photograph the usual silvery joints, the applied light sort of blurs-out the broken joints and makes them very difficult to see, even when fully blown up.  In order to capture this “trophy” to share with others, we applied a little black-light inspection magic borrowed from a machine shop, to highlight the extent of aging this board has received. 

 The process we used was to clean the board thoroughly, then apply a little penetrant to each of the solder joints.  After a couple of minutes, we wiped the excess penetrant off and cleaned the board again.  Next we applied the developer via spraying and almost immediately, the penetrant started flowing back out of the cracks and as you can see by the “green blobs”, became highly visible under the black light.  We then photographed all the joints while leaving the black light and the chemicals on.  This cuts down a lot of the glare, bouncing off the solder joints as well as lighting some of the areas a little from the mixed-in black light source.  Six of these 19 “bad” joints are attached on the collage and depending on which package of pictures you are looking at, some of the cracked joints as a full 8.5 by 11 inch printout.

 The glitching or intermittency seen in everyday operation or testing comes from cracks like these, sometimes making good connection, sometimes making ohmic connection and sometimes no connection at all, based on the ambient temperature and instantaneous vibrations.

 The vehicle that these shots came out of is a 1986 model and is pretty representative of the condition of the connectivity elements found in any other system that has seen this much service.  The one thing that was unique, was the high number of bad joints we found on such a small board and the ability of this vehicle to still deliver mostly satisfactory performance.  But like the people driving this vehicle experienced, keeping components like this on-board and by never finding or fixing these No Fault Found problems, occasionally your are going to be rather rudely surprised, whether in the air or on the freeway.

 Of course, other sources of intermittency are connector pins, loose terminal screws, crimp joints, wire wrap terminal, the wire that forms relay coils and other inductors, wipers inside potentiometers, inductive sensors, LVDTs, etc.  Just about everything has the potential to become intermittent due to the ravages of aging and abuse.

 “bench jockeys” and “bean counters” a better feel for the kinds of aging problems technicians and mechanics are running into on a day-to-day basis, trying to keep these electronic systems running and safe without having the proper equipment to find and fix them.