Refrigerator Won't Start? Starter Relay & Overload Kit (QP2 4R7 2‑Pin) — What Part Fixes This?
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Understanding the Problem
The compressor needs a momentary start boost to spin up; that boost is provided by a PTC starter relay (in this kit the QP2 4R7, a 4.7 Ω 2‑pin PTC) together with a thermal overload protector that disconnects the compressor if it draws excessive current. When either the PTC starter or the overload fails, the compressor may hum but not start, keep tripping on and off, or not run at all — leading to loss of cooling. Replacing the starter + overload kit restores the compressor's ability to start if the compressor itself is mechanically sound. The kit is a common and affordable repair for start-failure symptoms. However, a failed starter kit can also be a sign the compressor is aging or has a mechanical fault; if a new starter kit fails immediately or the compressor still won't start when the new kit is fitted, the compressor or wiring may need further diagnosis.
Common Symptoms
Fridge or freezer not cooling, compressor humming but not starting, clicking noise (relay cycling), intermittent cooling cycles, tripped breaker or blown fuses when attempting to start.
Common Causes
- Failed PTC starter relay (PTC has drifted open or no longer provides start boost)
- Open or shorted thermal overload protector (protects compressor from overcurrent/overheat)
- A weak or seized compressor that draws excessive start current and damages the starter/overload
Popular Parts That Fix This Problem
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Helpful Repair Tip
With power off, remove the starter and measure cold resistance across the PTC — it should be low (around a few ohms). Also check continuity on the overload (should be closed cold). If the PTC reads open or overload is open, replace the kit. Always disconnect mains before testing or replacing.
Frequently Asked Questions
Can I replace the starter relay and overload kit myself?
Yes, many do-it-yourselfers can replace the PTC starter and overload kit. Safety first: unplug the refrigerator or turn off the circuit breaker. Locate the compressor (usually in the back bottom), remove the protective cover or start-device bracket, note terminal positions, unplug the old parts and clip the new ones in the same orientation. Reattach covers and restore power. If you're not comfortable around mains wiring or compressor terminals, call a qualified appliance technician.
How do I test if the starter relay or overload is bad?
Turn power off. For the PTC starter, use a multimeter to measure resistance across the two PTC pins — a cold PTC typically reads a low resistance (in the single-digit ohms region for a 4.7 Ω part); an open/very high reading indicates failure. For the overload protector, check for continuity (cold it should be closed). You can also try a known-good starter kit temporarily: if the compressor then starts, the original starter/overload were faulty. If the compressor still won't start with a known-good kit, the compressor itself may be defective and needs further diagnosis.
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