Will GM Add a Fish Scale to It's Reliability Toolkit?

The GM Ignition switch failure may now be a criminal case.

The failure of GM to address the problem of the ignition switches failing leading to over 100 deaths has now lead to potential criminal charges being filed by federal prosecutors. What is most interesting about this case is that simple empirical non-destructive measurements would have provided discovery of the problem.

It is rare to have insight into any internal company history of serious electronic and electromechanical failures. Failure analysis and the causes of electronics or electromechanical systems failure can be a difficult investigation for any manufacturing company. Disclosure of the history and data is rarely, if ever, published due to the potential liability and litigation cost as is we are seeing in this case.

The report of the probe by former U.S. Atty. Anton Valukas issued June 2014 by the NHTSA on the failure of GM to determine the failure of air bags to deploy due to an ignition switch assembly is a fascinating case history. If you would like a copy of the redacted full 325 page report you can download it here.

Of course, a major player that misled the failure investigation was Ray DeGiorgio, who led the team that developed the switch and later approved a change to the part but failed to change the part number, which is against GM Procedures and good engineering practices. He also repeatedly denied making and approving a change to the spring and detent plunger that later improved the switch torque and eliminated the failures.

In the end, simple testing and empirical measurements of the torque required to rotate the switch and comparison of the force in several samples clearly showed the ease at which the switch could be moved from the “Run” position to the “ACC” position. This was discovered unintentionally when a GM Engineer trying to retrieve a BCM (Body Control Module), then noticed how unexpectedly easy it was to turn the key on one of the Cobalt model vehicles in a junkyard. The GM engineers then went to a local fish and tackle store to purchase a fish scale in order to measure the torque on the switches required to move it from the run position to the ACC position in "a number of Cobalt vehicles at the junkyard".

During design development of the switch it is almost certain that exceptionally low force to move the switch would have been found in a step stress test of several samples by increasing vibration, key chain weight until the point that the switch  rotates. 

It seems telling that actual testing of the device was a low priority throughout the years of investigation. Instead of using stress testing and comparing switch torque limits, GM tried reproducing the issue by simulating a worst case rough road driving test track but were unable to reproduce the failure mode with a relatively few samples. Testing many samples of switch assemblies to an empirical torque limit (the force necessary to rotate the switch), would have had a better chance of showing design flaw instead of a pass or fail test for a few samples on the “teeth chattering” test track.

It all reminds me of a quote from two known car experts and MIT Engineering graduates, Tom and Ray Magliozzi, who once on their NPR radio show “Car Talk” warned to be cautious of MIT Engineers understanding of actual devices operation because “they are never shown the actual ‘thing’ but are only given the mathematical models that describe the ‘thing’”. In the story of the GM Cobalt ignition switch there seemed to be little actual observation, testing, or empirical measurements on a device that was seemingly not hard to access since thousands were built and were easily accessible for a simple torque measurement that could be done in used and new car lots.

You can see many photos of the GM ignition switch assembly at the root of the problem from McSwain Engineering, Inc. at the International Business Times website link here.

Why not actually measure and compare product limits to discover variations and exceptions in design and manufacturing? Where have you seen that simple measurements would have discovered a reliability issue before it is manifested as widespread field failures?

Kirk Gray has over twenty-five years experience teaching, developing, writing and directing HALT and other reliability tests for rapid reliability development. If you like this post, you can find more about HALT and HASS empirical limit testing and contact information at Accelerated Reliability Solutions L.L.C.