My refrigerator died, most likely because of the starting relay+capacitor assembly which I already replaced once a few years ago. The parts store is closed today so I was curious and took the whole thing apart to find out exactly what broke down as this was sold as a "solid state" replacement, for which I find the lifespan rather short.

There is an obvious large capacitor, what looks like an overload protection and a third component which I presume must be the relay from the way it is wired. What leaves me puzzled is that it only has two connectors and is wired in series with the capacitor. What I've found online suggests the classic component here is a "potential relay" and should have a third connection. But this does not.

So of course I broke it open. I am including pictures of what I found: a mysterious circular disk (the component I'd like identified) sandwiched between two metal plates with springy contact points.

relay components clean side of the disk

The dirty side of the disk was in contact with the dirty plate. The disk has 40 ohms between the two sides, where clean. The dirty part appears non conductive and is, I suspect, why whe whole thing stopped working. Before being broken apart, the sandwich was a little loose and I could press the components closer together with my fingers. It seemed made so one side of the sandwich could slide. The case was typical electrical component plastic, similar to what the back of a wall outlet is made of.

So the question is: what is the disk and how does it make this thing into a relay or equivalent?

  • \$\begingroup\$ i had to replace that in my fridge ... the manufacturer called it "solid state staring relay" \$\endgroup\$ – jsotola Jun 3 '19 at 3:46

That above component is called Positive Temperature Coefficient relay. In this application it is uisng as starting device for compressor in your refridgerator. It is used for powering the start winding for a short moment to help starting up the fridge compressor motor.

what is the disk and how does it make this thing into a relay or equivalent?

The disk is the PTC thermistor material and the contacts and the plastics are for packaging and easy replacement.

Follow this link for more info.

  • 1
    \$\begingroup\$ This reference is pretty helpful. \$\endgroup\$ – David Schwartz Jun 3 '19 at 5:30

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