The "Er dH," also known as the Defrost Heater Error message, is displayed when the unit fails to reach 46? F within 2 hours of beginning its defrost cycle. This may be an indication of the defrost heater having broken or the temperature fuse having been pulled out of its slot. Contact customer service if the problem persists after having attempted a system reset.
Quick Fix

• Unplug the refrigerator for 30 seconds and then plug it back in. Doing this will reset all the codes. Sometimes an error appears by fault. If it does not appear again after restarting, then the refrigerator is fine. If the code appears again, then there is a problem with the defroster.
  

• The error code itself means that the defroster mode has failed. This means that the defrost mechanism cannot reach 46 degrees Fahrenheit within two hours to defrost ice in the freezer properly. Unplug the refrigerator and move all the items that can spoil into a backup fridge or freezer.
  

• Look in the back top of the freezer. Use a screwdriver to remove the ice maker machine that blocks the back defrost panel. Remove the two side screws and pull away the plastic cover guard. Check the wire. If it is unplugged, then secure it to see if that is the problem. If the plug is connected, then remove it to check for more problems. Look for any faulted wires on the defroster. If it appears that the wires are fine, you need to replace the defroster panel. Contact your local LG dealer for the specific part number