loud fan or refridgerator noise from front vent on 2004 mercdes s430
all working great but a loud sound (sounds like a fan or fridge running) coming from the fron vent. on a hot day it comes on after about 5 minutes but on a cool day it comes on about 30 minutes into driving. it does not shut off (shutting off auto climate control does not work). Only turning off the engine and taking out the key will stop the noise.....any guidance appreciated