When your vacuum is picking up dirt, the red light will come on. Occasionally, the lights may alternate quickly back and forth if the area is only lightly soiled or the dirt is spread out.
But, if you think that’s not the issue and the clean carpet sensor isn’t working, check the clean carpet sensor lens. If the lens is dirty, the sensor won’t perform properly. To clean the sensor lens, detach the Twist ‘n Snap Hose and gently wipe the clear lens area using a lightly dampened soft cloth. Allow enough time for the lens to dry thoroughly before reattaching the Twist ‘n Snap and using the vacuum.
If you still have problems with the sensor light, it might be best to take your vacuum to a technician. You can find your nearest BISSELL® Authorized Service Center by clicking http://www.bissell.com/support/product-support/service-centers or by calling 1-800-237-7691, available 24 hours a day.