You can test a fridge start relay with a multimeter by checking continuity/resistance on its terminals, but safety comes first: always unplug the fridge before touching anything near the compressor. A bad relay often shows no continuity where there should be one, or shows continuity where there should be none, and these faults directly explain why the compressor will not start and the fridge will not cool properly.
Safety and preparation
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Unplug the refrigerator from the wall.
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Locate the relay; it is usually a small cube‑shaped or cylindrical part clipped or mounted on the side of the compressor, with 2–3 wires plugged into it.
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Remove the back cover or panel to access the compressor, then disconnect the relay by gently pulling the wire connectors (not the wires themselves).
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Visually inspect the relay for burn marks, charring, or a rattling sound when you shake it; if present, treat it as faulty regardless of meter readings.
Set the multimeter
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Turn the multimeter to the resistance (ohms, Ω) or continuity range.
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For a PTC‑type relay (common on modern fridges), you will read a specific resistance value; for an electromechanical relay, the test is mainly “open/short” or continuity‑based.
Testing a PTC start relay (typical home‑fridge type)
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Identify the 2–3 terminals (often 2 pins on one side plus a center round terminal).
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Place one probe on each of the two “side” pins (often labeled 2 and 3) and read the resistance at room temperature.
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A healthy PTC usually reads several ohms (e.g., roughly 2–30 Ω depending on model; datasheets vary from about 2.8 Ω up to around 26 Ω).
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If the meter shows “OL” (open line / infinite resistance) instead of a steady low‑ohm reading, the PTC is faulty and should be replaced.
Testing an electromechanical relay (current‑type)
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Hold the relay in the orientation specified by its type (coil up or down) as per the label.
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For an EM‑type relay, check continuity between terminals 1 and 2; there should be continuity (low resistance / beeping in continuity mode). If there is none, the relay is bad.
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Then check between terminals 1 and 3 with the relay in the correct orientation; continuity should be present in one position and absent in the other (open when the relay should be open, and closed when loaded). If continuity is wrong in either position, replace the relay.
Quick‑check method for “universal” style relays
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Many small fridge relays have a center terminal (“common”) and two side terminals that connect when the relay is energized.
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With the relay still disconnected, place one probe on the center terminal and one on each side terminal in turn.
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You should read a low resistance (often below 10 Ω) between the center and each side terminal if the relay is good. If the meter shows “OL” on both side terminals, the relay is defective.
What the readings mean for cooling
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If the relay shows no continuity where it should (or intermittent/open readings), the compressor start winding will not energize, so the compressor may click but will not start, and the fridge will not cool.
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If the relay is internally shorted or stuck closed, the start winding can burn out or the compressor may overheat, also harming cooling over time.
When to replace and reassemble
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If the relay fails the continuity/resistance test or looks physically damaged, buy a replacement with the same type/number or a compatible universal relay.
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Reconnect the new relay, secure the cover, plug the fridge back in, and listen for the compressor starting normally; if it still does not start, the fault may lie in the compressor itself, overload protector, or elsewhere in the circuit.
Testing the start relay this way is a reliable way to rule one of the most common causes of “compressor does not start, fridge not cooling” before calling a technician or ordering a compressor replacement.