Combine chicken, carrot, celery, pepperoncini peppers, onion, ranch dressing mix, and au jus mix in a 3 ½- to 4-quart slow cooker. Pour broth over all.
Cover and cook on Low 5 to 6 hours or on High 2 ½ to 3 hours, until an instant-read thermometer inserted into the thickest part of the chicken thighs reads at least 165 degrees F (74 degrees C).
Remove chicken from slow cooker. Shred chicken with 2 forks.
Return shredded chicken and the egg noodles to the slow cooker. Stir in pepperoncini brine.
Cook on High about 30 minutes, or until noodles are tender.
Serve and enjoy.
