Here's the [document|42223|service manual] for the model.
On p.33 of 53 it shows the main control board voltage test points. The defrost heater is connected between P2/7 and P1/2. Check if there 120V AC across these terminals when the refrigerator is in the defrost cycle.
If there's voltage appearing there check if it is also at the heater connections.
Alternatively if you don't fancy testing for AC voltage, disconnect the power to the refrigerator and then disconnect the P1 and P2 harness cable plugs from the control board and then measure for heater continuity between the P2/7 and P1/2 pins ''on the cable plug (not the board)''
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If there's no voltage appearing at the heater connections (or continuity from the control board cable plugs) on p.34 it shows that there's an inline thermal fuse in the fan/heater/harness wiring between the heater connection and where the fan/heater wiring harness connects to the cabinet harness back to the control board.
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If there's no voltage appearing at the heater connections (or continuity from the control board cable plugs) on p.34 it shows that there's an inline thermal fuse in the evap fan/heater harness wiring between the heater connection and where the evap fan/heater wiring harness connects to the cabinet harness back to the control board.
Perhaps there's a faulty harness connection/wiring connection between the control board and the heater or the thermal fuse is faulty.
Hi @laurapage
Here's the [document|42223|service manual] for the model.
On p.33 of 53 it shows the main control board voltage test points. The defrost heater is connected between P2/7 and P1/2. Check if there 120V AC across these terminals when the refrigerator is in the defrost cycle.
If there's voltage appearing there check if it is also at the heater connections.
Alternatively if you don't fancy testing for AC voltage, disconnect the power to the refrigerator and then disconnect the P1 and P2 harness cable plugs from the control board and then measure for heater continuity between the P2/7 and P1/2 pins ''on the cable plug (not the board)''
If there's no voltage appearing at the heater connections (or continuity from the control board cable plugs) on p.34 it shows that there's an inline thermal fuse in the fan/heater/harness wiring between the heater connection and where the fan/heater wiring harness connects to the cabinet harness back to the control board.
Perhaps there's a faulty harness connection/wiring connection between the control board and the heater or the thermal fuse is faulty.