Stacy C Brentwood , TN May 05, 2019 Appliance: Whirlpool Rangehood UXT4230AAS0 Whirlpool Hood Uxt4230aas0: Exhaust fan knob was stripped and the filter was filthy. How to replace Charcoal Filter (Microwave Hood), 1 Filter. I ordered a new filter and knob, now I have a working knob and a clean filter. 1 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: Less than 15 minutes