Ice build up in back of fridge. I've done the drain clip change for the longer one but I'm getting ice buildup both at the top and at the bottom. I checked the heater with a multimeter and it shows 103.6 ohms so it seems to be fine. But when I put the fridge in FF/rd and Fd forced defrost modes the heater does not heat up.

I thought the sensor might be bad but would the sensor prevent the heater from heating up even in manual Fd modes??