How to Test a Refrigerator PTC Relay

Опубликовал Admin
18-10-2016, 23:30
6 505
A PTC (Positive Temperature Coefficient) relay is a starting device for fridge compressors. It is responsible for powering the start winding for a brief moment to help start up the fridge compressor motor. If your fridge cannot start there is a high probability that the PTC relay is defective. This article presents how to test them to determine whether they need replacing. Luckily, these common fridge parts are relatively inexpensive and easy to replace.


  1. Expose the back of the fridge to get access to the motor. Make sure the appliance is unplugged.
  2. Find the fridge compressor and remove the plastic case that houses the starting circuitry. Either memorize the wiring or take a few pictures just to be sure you know how to put it all back together when you're done. There's usually a diagram somewhere as well - make sure you can follow it and identify parts.
  3. Find the PTC relay. It is plugged onto the 3 prong connector on the side of the fridge compressor. Turn it over to expose its bottom side and locate the connectors - most have 3 sockets but some only two.
  4. Shake the PTC relay. If you can hear something rattling inside, it suggests that it might be broken.
  5. Inspect the part visually and smell it. Burnt out marks or smell are another indication of a broken part. Shaking and inspecting visually are not good enough methods - proceed to the next step to be sure.
  6. Use a multimeter to measure resistance across all the pairs of the connectors on the underside of the PTC relay. Only one pair should give you a reading - it should be between 10 - 100 ohms. If you can't get any reading at all make sure you set the multimeter on the lowest resistance or Continuity range and repeat the measurements. If you still get no indication of continuity, the PTC relay is broken.
  7. If you determined that it is broken, note the part number and order a replacement.


  • It is advised to test the windings of the compressor as well.


  • Make sure the power cord is unplugged.
  • Always pay special attention when working with electric appliances.
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