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Ope!  Another story.  Circa 2007.  One of our controller suppliers - based out of British Columbia - had a quality issue with one of the chips on their main board.  When the temperature dropped to around freezing - the systems would reset.  You would think a company based in BC would be able to design something that worked in the cold - because it gets cold in BC.  Right?
Unfortunately, this meant that the system also went into Emergency Stop - which required a manual reset.  This is not a good condition for an emergency backup generator.  Of course, they initially denied it.  So I took a dozen of the controllers and placed them in the refrigerator freezer at work and took them out one by one for testing.  At least 1 in 4 failed - so I threatened to ship 100% of our stock back and replace them with a different supplier.  We never did figure out which chip was the root cause of failure.

Story 2:  Home standby generators would not make voltage when the temperature dipped to 20F or so.  That's not all that unusual a temperature for Wisconsin or any of the Northern states.  It happens from time to time in the Southern states.  The generators would fail.  We would replace the voltage regulator.  They would fail again.  We would bring them to the shop.  They would not fail.  Any of them.  It took us weeks to figure out that the component supplier had changed potting material - that shrank when it got cold - and was pulling the connections on the PCB open.  They would reconnect once the potting material expanded when it got warmer.
  While the system manufacturer blamed a supplier, we all knew that these regulators were made in house.  

Story 3:  Sort of the same thing as above - except this time it was an internal connection on a Silicon Controlled Rectifier.  Once the temperature got to below freezing, the Gate would open.  This was even harder to track down because there are 6 SCRs in a 3-phase full-wave bridge rectifier and, depending upon the load (or lack thereof - aka testing), two functional SCRs can mask the problem for a long time.  We did learn that the manufacturer changed suppliers - and wrote a better specification for the rectifier assembly.

Ope!  Another story.  Circa 2007.  One of our controller suppliers - based out of British Columbia - had a quality issue with one of the chips on their main board.  When the temperature dropped to around freezing - the systems would reset.  You would think a company based in BC would be able to design something that worked in the cold - because it gets cold in BC.  Right?
Unfortunately, this meant that the system also went into Emergency Stop - which required a manual reset.  This is not a good condition for an emergency backup generator.  Of course, they initially denied it.  So I took a dozen of the controllers and placed them in the refrigerator freezer at work and took them out one by one for testing.  At least 1 in 4 failed - so I threatened to ship 100% of our stock back and replace them with a different supplier.  We never did figure out which chip was the root cause of failure.

Story 2:  Home standby generators would not make voltage when the temperature dipped to 20F or so.  That's not all that unusual a temperature for Wisconsin or any of the Northern states.  It happens from time to time in the Southern states.  The generators would fail.  We would replace the voltage regulator.  They would fail again.  We would bring them to the shop.  They would not fail.  Any of them.  It took us weeks to figure out that the component supplier had changed potting material - that shrank when it got cold - and was pulling the connections on the PCB open.  They would reconnect once the potting material expanded when it got warmer.
  While the system manufacturer blamed a supplier, we all knew that these regulators were made in house.  

Story 3:  Sort of the same thing as above - except this time it was an internal connection on a Silicon Controlled Rectifier.  Once the temperature got to below freezing, the Gate would open.  This was even harder to track down because there are 6 SCRs in a 3-phase full-wave bridge rectifier and, depending upon the load (or lack thereof - aka testing), two functional SCRs can mask the problem for a long time.  We did learn that the manufacturer changed suppliers - and wrote a better specification for the rectifier assembly.