How often does a defrost timer cycle? Kitchenaid KSSS42MWX00

Refrigerator & Freezer Repair
1

Brand:Kitchen Aid
Model Number: KSSS42MWX00
Main Symptom:Freezes up
What happens & when:Sporadically (weeks apart)

Error Code (if any):
Parts or tests already tried:
Photos / video link:

2

For your KitchenAid KSSS42MWX00, the defrost system is controlled electronically rather than by a traditional mechanical defrost timer.

The refrigerator uses an adaptive defrost system, meaning it doesn’t necessarily defrost at the same interval every day.

Typically:

  • Defrost interval: Approximately every 8–12 hours of compressor operation, although the interval can vary based on operating conditions.
  • Defrost duration: Generally 20–30 minutes, depending on when the defrost thermostat opens and how the control manages the cycle.
  • Normal operation: The compressor and evaporator fan shut off while the defrost heater melts frost from the evaporator coils.

These are general operating ranges, not confirmed factory specifications for this exact model.

Since it’s freezing up weeks apart

I’d check these items before replacing the electronic control:

  1. Defrost heater: Unplug the refrigerator and check resistance. An open reading (OL) indicates a failed heater.
  2. Defrost thermostat (bimetal): Test it while it’s still cold and covered in frost. It should show continuity when closed.
  3. Evaporator frost pattern: If the entire evaporator is packed with snow or ice, suspect a defrost problem. Ice concentrated around an air opening may indicate an airflow or moisture problem.
  4. Electronic control: If the heater and thermostat test good, check whether the control is initiating defrost.

One important question

When you say it freezes up, is the freezer evaporator coil completely covered in frost, causing the refrigerator section to get warm, or is food actually freezing inside the refrigerator compartment?

That distinction will help determine whether we’re dealing with a defrost failure or a temperature-control problem.

3

Thanks for the background. I don’t see any electronics and have just replaced the timer as the most likely culprit.

I have had this refer for 20+ years and freeze ups were originally rare and associated with door seal problems. 8 years ago a pro changed out the timer “just in case”. 3 years ago the same pro swapped out the heater and bimetal, commenting that it was time to buy a new refer ($10k). The current rash of freeze-ups started 6 months or so ago.

4

Yeah, this refrigerator has a timer for defrost.Here is the tech sheet and parts list!
KitchenAid KSSS42MWX00 Refrigerator Tech Sheet-1113730.pdf (1.1 MB)
Part List - 4361001 - Rev B.pdf (491.9 KB)
instructionsheet-482494-revr.pdf (403.3 KB)
Make sure the timer wire that has the loose lead goes to terminal 2 on the Defrost Timer: