Embraco Compressor Start Relay Kit FAQ: Why Your Small Chest Freezer Clicks but Won't Run

I'm a quality manager at a refrigeration parts distributor. I test compressor relay kits, condensing units, and replacement compressors before they go on the shelf—roughly 200 part numbers a year, and I've rejected more than a few of them in incoming inspection. If you've searched for an "embraco compressor start relay kit" or looked up the NT6215Z compressor, these are the questions you'll want answered.

Here's what this article covers:

1. My Embraco compressor clicks but won't start. Is the relay the problem?
2. OEM Embraco relay kit vs. a universal relay: does it matter?
3. Is the NT6215Z the right compressor for my small chest freezer?
4. How do I clean condenser coils, and why does it affect the relay?
5. My window fan runs fine. Why does my freezer need a relay at all?
6. The cheap relay ships in two weeks. Is rush shipping worth it?
7. How do I know if I need a new compressor instead of a relay?

My Embraco compressor clicks but won't start. Is the relay the problem?

Usually, yes—well, the relay is the component that fails, but it's not always the root cause. A clicking sound from behind a small chest freezer is the start relay trying to kick the compressor into run and dropping out. In our Q1 2024 warranty audit, roughly 70% of "won't start" returns traced back to the relay kit itself.

But here's the part people miss: relays don't just die of old age. They fail from repeated high inrush current, and high inrush is often caused by a compressor that's struggling. A struggling compressor is frequently caused by dirty condenser coils—more on that in question four.

Before you order anything, unplug the freezer and take the cover off the relay on the side of the compressor. Look for scorched terminals or a burnt smell. No visible damage? Test for continuity across the relay; no continuity means it's time for an Embraco compressor start relay kit.

OEM Embraco relay kit vs. a universal relay: does it matter?

To me? Yes. I ran a bench test once with a universal "3-in-1" hard-start device and an OEM Embraco compressor start relay kit side by side. The universal part started the compressor—barely. Its contact resistance measured nearly double the OEM specification, and after 50 cycles it was noticeably hot. The OEM relay was still within spec after 500 cycles.

Seeing that comparison side by side made me realize why "compatible replacement" is a dangerous phrase. It's compatible in the sense that the terminals fit. But the electrical specs—pull-in voltage, dropout, thermal budget—are what actually protect the compressor. A $7 universal relay that fails in six months costs more than a $25 OEM kit, because you'll pay for a second diagnosis and a second service trip.

I do not mean universal relays never work. They save the day sometimes. I mean an OEM-matched kit gives you certainty, and certainty is worth real money when the alternative is a warm freezer.

Is the NT6215Z the right compressor for my small chest freezer?

The NT6215Z is a low-back-pressure (LBP) compressor, which means it's built for freezer and low-temperature applications. For most 5 to 10 cubic foot chest freezers, that's the right compressor family. Rated performance is measured per AHRI Standard 540—the same benchmark most datasheets use—so you can compare models on equal footing.

I want to say the capacity is roughly 600 to 800 BTU/hr at -10°F evaporating, but don't quote me on the exact figure. The rated number depends on the refrigerant and where you measure it, and the datasheet for your specific version is the authority.

What you need to verify before buying: the label on the old compressor. Check the model stamp, voltage (115V for North American chest freezers), and the refrigerant printed on the system nameplate. Versions of the NT6215Z have shipped in different OEM configurations, so match the replacement to the system's refrigerant and electrical specs—not to the freezer brand. Swapping in a high-back-pressure A/C compressor because "it fits" is the fastest way to overheat and cycle on thermal overload until it dies.

How do I clean condenser coils, and why does it affect my Embraco compressor?

For a small chest freezer with exposed rear coils: unplug it, pull it away from the wall, and use a soft brush and a vacuum with a crevice tool to lift the dust off the coils. Work top-to-bottom, and don't bend the fins. Do this every six months for a home unit, every quarter if it sits in a dusty garage or a commercial space.

I only believed this mattered after ignoring it. In early 2024, the condenser coils on our shop's backup freezer were packed with dust. The NT6215Z compressor inside kept clicking off on thermal overload. I tested the relay, the capacitor, the windings—everything. Only after I blew the dust out did the amp draw drop and the compressor run a full hour without tripping. It was kinda embarrassing.

Why does this matter for the relay? Dirty coils raise head pressure. Higher head pressure makes the compressor draw more current. More current degrades the start relay contacts every time it starts. So if you replace a relay without cleaning the coils, you're just starting a timer for the next failure.

My window fan works fine. Why does my freezer compressor need a relay at all?

Different motors, different jobs. A window fan uses a shaded-pole or PSC induction motor—it starts up on its own, which is why nobody ever sees a fan "fail to kick over." A hermetic refrigeration compressor has to start under load. The refrigerant inside the sealed system pushes against the piston before the motor can build speed, so the motor needs high starting torque.

The start relay makes that happen. It connects the start winding, the compressor builds torque, and once it reaches speed, the relay drops out. No relay, no start.

It's tempting to think of a compressor as "a tougher, louder fan motor." That oversimplification is exactly why people get confused when the fan spins but the compressor clicks. The moving air is irrelevant to the starting problem—the relay is what handles the heavy lifting, and a fan motor just doesn't need one.

The cheap relay ships in two weeks. Is rush shipping worth it?

When the freezer is empty and nobody depends on it, no—save the money. When it's a restaurant's prep freezer holding product for the weekend, absolutely. The extra $15 or $20 for overnight delivery on a start relay kit is not buying speed. It's buying certainty about when the problem gets solved.

In July 2024, a client paid $18 extra for next-day delivery of an Embraco relay kit for a small chest freezer. The alternative was a $6 generic part that might arrive in five days and might meet spec. The freezer was holding $3,000 of food at 28°F and climbing. The FDA Food Code recommends frozen storage at 0°F or below, so that product was already on a deadline. Spending $18 to protect $3,000 is not a hard decision.

I've been burned twice by "probably on time" promises. "Probably" is the risk. A cheap part with an uncertain delivery date is more expensive than a certain one, because being wrong means a second service call, a second diagnosis, and more warm food. I'm not telling you to always rush parts. I'm telling you the premium is worth it when the cost of delay is real.

How do I know if I need a new compressor instead of a relay?

Run through this order before you replace anything:

1. Check the outlet voltage. Low voltage—below the compressor's rated minimum, typically around 104V for a 115V unit—causes the exact same clicking symptom.
2. Test the compressor windings with an ohmmeter. Compare Common-to-Run and Common-to-Start resistance against the datasheet. An open or shorted winding means the compressor itself is done.
3. Listen for a hum. A locked rotor sounds like a relay problem, but it isn't. The relay is working; the compressor can't turn.
4. If the compressor runs but the freezer won't get cold, stop testing components. That's a sealed-system issue—leak, restriction, or weak valves—and opening the sealed system requires EPA Section 608 certification. As of January 2025, that's still the rule; verify current requirements at epa.gov.

If the windings are dead, replacing the compressor is a valid repair only when the appliance is worth it. A 15-year-old 7 cubic foot chest freezer might not be—an efficient new freezer can beat the cost of a compressor, relay, and two service visits. The honest answer is sometimes "buy new," and it's my job to say so instead of pushing parts.