Step-by-step fix
Step 1: Confirm the center mullion heater strip is the likely problem
- Look at the center divider between the fresh-food doors or between the refrigerator and freezer door openings, depending on your layout.
- Check whether the moisture or sweating is concentrated along that center mullion area rather than around the whole door perimeter.
- Touch the mullion after the refrigerator has been running normally. It should often feel slightly warm, not cold and damp all the time.
- Inspect the door gaskets for tears, gaps, food buildup, or a door that does not close fully, since those problems can also cause sweating.
- Make sure the room is not unusually humid and that the refrigerator doors are not being opened constantly, which can mimic a heater-strip problem.
If it works: You have a centered sweating problem and the mullion area does not seem to be warming as it should.
If it doesn’t: If moisture is mainly around a door edge, fix the door gasket or closing issue first. If the whole cabinet is sweating in very humid weather, reduce humidity and recheck before replacing the heater strip.
Stop if:- You find broken door hinges, badly warped door gaskets, or cabinet damage that is clearly causing the moisture problem instead.
- You smell burnt wiring, see melted trim, or notice exposed damaged wires around the mullion area.
Step 2: Unplug the refrigerator and clear the work area
- Move food or bins only if they block access to the center mullion trim or interior cover you need to remove.
- Unplug the refrigerator from the wall outlet before opening any trim or disconnecting any wires.
- Dry the center mullion and nearby surfaces with a towel so you are not working around standing moisture.
- Put on gloves and keep screws and clips in a small cup or tray so nothing gets lost.
If it works: The refrigerator is unplugged, the area is dry, and you can reach the mullion trim or access point comfortably.
If it doesn’t: If you cannot safely reach the plug, switch off the correct circuit and verify the refrigerator is off before continuing.
Stop if:- You cannot disconnect power safely.
- The refrigerator must be pulled out in a way that risks damaging the floor, water line, or power cord without help.
Step 3: Remove the trim or cover and expose the heater strip
- Inspect the center mullion area for visible screws, snap-in trim, or an interior cover that hides the heater strip connection.
- Remove screws first, then gently pry trim loose a little at a time to avoid cracking plastic.
- Take a quick photo of the wire routing and connector position before disconnecting anything.
- Follow the heater strip leads to their connector or terminals and disconnect them carefully without yanking on the wires.
- Lift or slide the old heater strip out of its channel, adhesive track, or retaining clips, depending on how your refrigerator holds it.
If it works: The old heater strip is out and you know how the wiring and trim were originally routed.
If it doesn’t: If the strip seems stuck, look again for a hidden screw, clip, or adhesive section before forcing it.
Stop if:- The liner, mullion frame, or trim starts cracking under light pressure.
- You uncover corrosion, water-damaged insulation, or wiring damage beyond the heater strip itself.
Step 4: Install the new refrigerator center mullion heater strip
- Compare the new heater strip to the old one for overall length, connector style, and mounting layout before installing it.
- Set the new strip into the same channel or mounting position as the original so it sits flat and does not twist.
- Reconnect the wiring firmly, matching the original routing so wires do not get pinched by trim or rub against moving parts.
- Reinstall any clips, covers, or screws that hold the strip in place.
- Press trim back evenly and make sure it seats fully without bulging.
If it works: The new heater strip is mounted securely, connected properly, and the trim is back in place without pinched wires.
If it doesn’t: If the new part does not match the old one closely enough to mount and connect the same way, pause and verify the replacement using your refrigerator model information.
Stop if:- The connector is loose, overheated, or will not mate securely with the new part.
- The new strip cannot be installed without forcing trim or bending the part unnaturally.
Step 5: Restore power and let the refrigerator run
- Plug the refrigerator back in and confirm it starts running normally.
- Close the doors and give the refrigerator time to resume normal operation.
- After some run time, check the center mullion again by touch. It should begin to feel slightly warm rather than cold and clammy.
- Wipe away any leftover moisture so you can tell whether new condensation is forming.
If it works: The refrigerator is running again and the mullion area is beginning to warm up.
If it doesn’t: If the refrigerator runs but the mullion still stays completely cold after a normal run period, recheck the connector and part fit.
Stop if:- The refrigerator does not power back on after reconnection.
- You hear arcing, smell hot plastic, or notice the trim heating unevenly or excessively.
Step 6: Verify the repair holds in normal use
- Use the refrigerator normally for the rest of the day and check the center mullion area a few times.
- Look for a clear reduction in sweating, water beads, or dampness around the center divider.
- Confirm both doors still close and seal properly after the trim was reinstalled.
- Keep an eye on the area during a humid part of the day, since that is when a failed mullion heater usually shows up fastest.
If it works: The center mullion stays mostly dry in normal use and no new condensation builds up around the divider.
If it doesn’t: If sweating continues, check for a weak door gasket seal, frequent door opening, or a wiring/control issue that is not powering the heater strip.
Stop if:- Condensation is still heavy after the new strip is installed and the doors seal well, which points to a different electrical or airflow problem.
- You see water tracking from above or from inside the cabinet, suggesting a separate leak rather than a mullion heater issue.
Replacement Parts
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FAQ
What does a refrigerator center mullion heater strip do?
It adds a small amount of heat to the center divider so humid room air does not condense into water on that surface.
How do I know the heater strip is bad instead of the door gasket?
A bad heater strip usually shows up as sweating focused on the center mullion while the door gaskets still look intact and seal well. If moisture is around the outer door edge, the gasket is a more likely cause.
Should the center mullion feel hot?
No. It usually feels just slightly warm. If it is completely cold and damp during normal operation, the heater strip may not be working.
Can I keep using the refrigerator with a failed mullion heater strip?
Usually yes, but the center divider may keep sweating and can leave water on the trim or floor area. It is better to fix it before moisture causes staining or wiring corrosion.
Why is the mullion still sweating after I replaced the heater strip?
The new part may not be getting power, the connector may be loose, or the real cause may be a poor door seal, very high room humidity, or another refrigerator control problem.