A refrigerator timer, also known as a defrost timer, is a device which is used to regulate the amount of frost in a refrigerator. It turns on periodically to allow frost in the fridge to melt so that a frost buildup does not occur. Most modern refrigerators use a timer to keep their frost levels relatively stable. If a fridge starts to accumulate frost, doesn't cool properly, or is too cold, these can be signs that the timer is defective and needs to be replaced.
This device can be located in a number of different locations inside the fridge, including behind the control panel or grille in the freezer. It is a crude clock which switches back and forth between a defrost mode and a regular cooling mode. When the refrigerator timer turns into defrost mode, the cooling functions of the refrigerator are turned off and the defrost heater is activated to melt frost which has built up in the freezer. When the timer returns to cooling mode, the refrigerator is allowed to cool again and the defrost heater is turned off. The overall internal temperature of the fridge is kept in a safe range.
Historically, people had to defrost their refrigerators by hand. This involved emptying the refrigerator, unplugging it, and allowing all the ice inside the melt. In addition to being a time consuming process, this could also be a food safety issue, because foods might become dangerously warm while they were held outside the refrigerator. For this reason, many companies began developing so-called “frost free” refrigerators which use a refrigerator timer to regulate the defrosting process.
The refrigerator timer can eventually fail. People can test their timers with the assistance of a multitester. Power to the fridge should be cut so that the device can be removed. Then, one probe on a multitester can be applied to the common terminal (often marked “C” or “3”) on the refrigerator timer. The other probe can be applied to one of the three remaining terminals on the timer, one at a time to get a reading for each terminal. The readings for one to two of the terminals should be “zero,” while the other one or two should read “infinity.” When the refrigerator timer is manually adjusted to the other setting, these readings should be reversed. If the readings do not follow this pattern, the device needs to be replaced.