[AllanC]

99 Cirrus, with cruise control that works 25% of the time. The other 75% of the time, when set , the dash light comes on but does not hold speed and turns off. Replaced with another unit, same result. Would think it is a vacuum problem, except it does work once in a while. It could be a wiring short, but that typically does not happen often. Any suggestions?

When the cruise control is NOT operative, does the instrument panel lamp CRUISE illuminate? If the lamp does not turn on then I would suspect that there is an open circuit in the clock spring wire in the steering column. Even when the cruise system is operating, the circuit in the clockspring wire must maintain continuity at all times for the control function to operate properly. You turn the steering wheel slightly, the clockspring wire for the cruise circuitry opens, the powertrain control module detects this and disengages the cruise function.

Start the engine and let it idle. Push the on / off toggle switch or button and see if the word CRUISE illuminates on the instrument panel. It should turn on even if the vehicle is not moving. If it does illuminate turn the steering wheel several times full left and full right and see if the cruise lamp stays on. If it turns off with steering wheel movement, you have pinpointed an intermittent circuit in the clock spring wire.