Defrost Timer Test

[TennilleGuy]

I have read the How-to appliance file "How to Test the Defrost Timer" and I am confused. The file says first to "locate the common terminal, it should be labeled "3" or "C"...it is usually the white wire." It then asks you to place one multimeter probe on the common and the other on one of the other three and proceed according to the rest of the test. I did so for the original defrost timer of the freezer in my Sub-Zero 532 side-by-side. It has a white wire and it is labeled "3". The timer failed the test. It passed the test, however, if I used the black (hot) wire (labeled "1"). I purchased a replacement timer (part no. 3081180) and when it arrived I gave it the same test using the "3" terminal with the others as described in the How-to test. It also failed the test. But it, too, passed the test using the "1" terminal. My question? Is the test description wrong? Or, is this particular defrost timer different from others?

[DIY Guy]

We've tested defrost timers here in our offices and we've referred to technical manuals. They all agree with the instructions as posted.

The defrost timer is essentially a switch. It cuts power to the fan and sends power to the defrost heater. So in the normal setting, two pairs should have continuity (in some cases one pair) and in defrost mode two pairs should have continuity but one of the pairs should have swapped with with one of the pairs from the first test that had infinite continuity.

We would be interested to know exactly what test results you got with your Sub-Zero defrost timer. There may be something unique about it. If so, we'll add the details to our article for our readers.