A controller for monitoring an air system in a vehicle comprises an input for receiving at least one pressure signal indicative of an air pressure in an air system an output for transmitting an alert to a vehicle operator; and control logic. The control logic is capable of determining an instant cut out time indicative of the time for the at least one air pressure signal to reach a cut out pressure value from a cut in pressure value; determining a difference between the instant cut out time to an average cut out time; and transmitting a leakage alert at the output in response to the instant cut out time being greater than or equal to a predetermined difference from the average cut out time. The control logic is also capable of changing the compressor operation in response to the alert.