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Replacement parts for General Electric ZISW42DSB Refrigerator | AppliancePartsPros.com

Does sound like a defrost problem.

First open it up so you can see the coils.
Do not let them de-ice.
If they are heavily iced/frosted over you have a defrost problem.

If yes.
Manually force a defrost cycle by turning the defrost timer cam (Item 7405 in Section 6) till the fans and compressor turn off.
Now check the defrost heater to see if it is on.
Be careful you do not want to burn your fingers.
If the heater is on then the timer needs replacing, re: it is probably stalling during it's rotation so is never getting into a defrost cycle.

If not on.
Unplug the unit.
Remove the wire for one side of the heating element (Item 245 in Section 2) from the wiring and measure it for continuity, usually around 20 ohms or so.

If the heater is OK
Remove one wire to the defrost thermostat (Item 12 in Section 2) and measure it, should be 0 ohms when frozen. Note that it opens just above freezing so must be frozen to check it. Also inspect it, if it is bulged at all replace it even if it measures OK.

If both the above are OK then odds are the defrost timer contacts are toast.
Best way to test this is a live test to see if you have 120 volts across the heater/defrost thermostat combo.

The resistance across the heater is 4.5 ohm
here is something weird with the above.
It seems way too low to me, 4.5 ohms would draw 27 amps.

To replace the defrost thermostat you have to gain access to the evaporator coils as it is clipped onto the coils.
I am not sure how to do this.
With luck someone else will jump in with that info.

You are welcome.

And thanks for getting back to us, now when others search they will see what actually fixed the unit instead of just suggestions about the possible cause.