The Case of the Condemned Generator


A large aerospace company in Kansas owned a large industrial generator that wasn’t generating; it was subsequently sold to two different companies — neither of which could make it work —so the generator was condemned.


The first thing the ACES Control Systems Investigator noticed was that the engine starter was missing. No direct replacement was available from the parts distributor, but with some maintenance and hand cranking the engine was running again.

The next hurdle was the lack of generator output. After some additional sleuthing the CSI discovered the exciter brushes were stuck. Repairing the brushes brought the generator back online, but now came an even deeper puzzle: The generator wouldn’t run in automatic mode.

The CSI needed to diagnose the wiring. The manufacturer couldn’t locate a wiring diagram so the CSI diagramed the unit himself. The control panel had multiple sealed relays and electronics so he began by drawing the relays, and then developed his own diagram.


As he came to understand how the system worked the CSI deduced that a technician at the aerospace company had replaced the SPDT (single pole double throw) switch for the AUTO/MANUAL option; the technician had swapped the common and one switch leg, preventing the unit from starting in automatic mode. This probably led the technician to remove the starter for repair.


The ACES CSI studied many different starter specifications and identified a starter that fit the geometry of the engine. He correctly rewired the AUTO/MANUAL switch, and now the entire system hums along, generating electricity in both auto and manual modes.

Every day millions of dollars worth of industrial and municipal equipment are condemned to the scrap heap because of a minor problem. Finding a company that can investigate and solve these small but challenging mysteries is increasingly difficult, but they are out there. ACES is one of them.