Q&A for How to Test a Refrigerator PTC Relay

Either you have a bad connection somewhere in your wiring, including your plug for the refrigerator, or your compressor is internally dragging, causing a high amp load. In my experience, having a "newer" refrigerator does not necessarily mean your are immune to this. The fixes are new compressor or new fridge.

It seems you are reading the PTC or thermistor, not the contacts. One should read zero ohms, which is a dead short. Because you aren't getting a dead short on any test, you either have a bad relay or you aren't testing properly. The thermistor is electrically between the contacts of the relay, in parallel with the relay contacts.

Yes, it can cause greater amp usage and prolonged running time for the compressor. Eventually the relay will go out.

Check supply voltage. If supply voltage is in between 160- 170 Volts, then there should be the problem of low voltage. Please connect starting capacitor of 5mfd, 400volt parallel to ptc relay.

You cannot. The relay is there to let the compressor windings start on one winding and then almost immediately switch to the second winding. Most high load or heavy load applications have this start then run mode.

It can be. If the windings don't burn up, there will be current causing heat to be in the wiring. Since there is a lot of wire in windings, the compressor can be extremely hot. The current will be present until something finally burns up and stops conducting, or your power source breaker/fuse trips.

No, the compressor contains all the gasses that make the air con function.

There's a pretty simple shake test you can try to see if your relay is bad. Unplug your fridge so there isn't any power running through it. Use a screwdriver to take off the screws holding the lower back panel on the back of your fridge in place and remove the panel. There may be a plastic cover you need to remove to expose the relay. Pull out the 2-3 wires in the relay with a pair of needle nose pliers, then remove the relay. Look for burnt marks around the ports on the relay to see if it’s shorted. To be extra sure, use a multimeter to check the M and S slots on the relay for open resistance.

A positive temperature coefficeint relay, also known as a PTC or a start relay, starts the compressor inside of your fridge. The compressor is what creates the cold air that keeps your refrigerator cold. So, if your fridge stops making cold air, there could be a problem with the PTC relay. The first place you should check when your fridge isn't cold anymore (after making sure the power is turned on) is the PTC relay, which is easy to replace if there's a problem. If there isn't anything wrong with the relay, there could be problem with your compressor, which is a much more costly and complicated fix.

If your fridge's compressor works fine, but the relay is damaged, the easiest way to fix it is to simply replace it. Start by unplugging your fridge and pulling it away from the wall so you can access the back. Use a screwdriver to remove the small access panel on the back and look for the compressor inside your fridge, which will be a large black cylinder on either side of the machine. Look for a small plastic box on the side of the compressor with 2-3 wires sticking out of it. Use a pair of needlenose pliers to remove the wires, then pull the relay off of the compressor. Plug a new relay into place and reconnect the wires in the same order. Then, replace the panel, plug in your fridge, and test it out.