If they say rack and pinion it could be there's a leak coming from the rack and pinion. If it was the alternator it would most likely be bad pulley bearings which would cause it to make more of a squeel or metal on metal grinding. You said it continues to happen while the car is not moving but the engine is running correct?
1999 Chevrolet Camaro SS (PC'd)
1994 Chevrolet Beretta Z26 Q4 (W41 M90'd)
2004 Chevrolet Silverado 2500 (4WD)
My wife's cars:
1971 Dodge Charger SE (stock and original 383 auto)
2004 Subaru Impreza WRX (kid-hauler)