1992 Cadillac Deville air shocks

The factory air shocks automatically adjust with a pump located under the hood. After rotating the tires I found that the shocks did not pump up or adjust any more (pump did not turn on). It is my understanding that there is a leveler switch (located somewhere near the rear of the car) that operates the pump, as necessary, to raise the rear of the car. Do you happen to know where this switch is, if this could be responsible for the pump not operating, and how to clean it if it is responsible?