I have a Frigidaire top freezer refrigerator. The freezer is fine, however it freezes up and blocks the vent, preventing cool air from circulating into the refrigerator section: Pic attached is freezer interior: enter image description here


  • Ice builds up on back panel of the freezer.
  • Air vent into fridge gets blocked by this ice.
  • Fridge doesn't cool down.

A few things I have tried:

  • Defrost heater is reading 35 ohms.
  • I have noticed the fridge enter its defrost cycle throughout the day.
  • Manually turning the mechanical defrost timer does send the unit into defrost.
  • When I trigger the defrost, the heater does warm up and glows red.
  • Ventilation fan is working.

What could be the problem here, or what should I check for?

The thermostat should be okay, since it turns on the heater once the defrost cycle is on. There is no problem with the defrost heater. The only other thing that could be the problem is the defrost timer. However it does activate the defrost cycle throughout the day that I've noticed. Could it still be faulty?

2 Answers 2


three main points come to mind (in this order):

  1. Door seal(s): even though you may think the door is closed all the way, a weak magnet or bad seal will cause this problem EVERYTIME. Try the "dollar bill" trick: place a dollar bill in the area around the door seal and do a full series of tests the full perimeter of the door. The dollar bill should be held in place by the door seal when closed and should require effort to pull it out. If it is "easy" anywhere, then the seal is poor and moisture is getting in greatly accelerating frost buildup
  2. Air fan: While you identify the fan is working, is it working properly? The motor itself can be marginal, running poorly, or not at all, check contacts and wiring, and also confirm the bearings are firm but the blades spin freely. Also (and this is critical), ensure the supply and return ducts are not blocked. Make sure they are fully defrosted, and clean. Any food, mold, plastic bags, etc are removed and do not store products in front of or blocking the ducts
  3. Refrigerant cycling: if there is a flow issue (pinched lines etc) or too low refrigerant, the unit can be cycling on and off or never off, either way allowing the ice buildup, but this is usually only found in old or damaged units. Try setting the freezer to its warmest acceptable level, and make sure it is cycling off vs. running 24/7

As noted in the other answer, but amplifying it a bit further, make sure that if the unit has a defrost tray that it has water in it - it is possible the ductwork is bloxked by plastic debris or mold/food. Make sure all tubing is free and clear

  • Try cleaning the drain with a turkey baster filled with hot water. Caution be sure you know where the water goes, on some units it is in a small pan thing where the compressor heat evaporates it and it can overflow if you are not careful.
    – Gil
    Commented Jul 8, 2021 at 16:58

I had similar problem. The fix for me was to unplug the drain so the water that is gathering under the radiator has a chance to escape from the fridge.

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