Embraco Start Relay Wiring Diagram

Wiring an Embraco Start Relay Without Losing Your Mind

I spent three hours on a fridge that wouldn't start, only to discover the relay was making perfect contact but the capacitor was dead. The Embraco start relay itself was fine. It happens more than you'd think when you're knee-deep in a tight compressor bay and everything looks the same from the outside. Here's the actual setup. Embraco uses a few different relay types depending on the compressor model, but the PSC (permanent split capacitor) with start relay configuration is by far the most common in residential refrigeration. The relay clips onto two of the three compressor terminals and the capacitor bridges the remaining pair. The three compressor terminals are labeled S (start), R (run), and C (common). On Embraco compressors these are usually arranged in a Y pattern when you're looking at the terminal plate face-on. S is typically on the left, R on the right, and C at the bottom center. Don't trust the positions blindly though — I learned that the hard way on a BTU4000 series where the layout was flipped compared to the manual.

The start relay itself has a simple job: it pulls in an initial current surge through the start winding to get the rotor moving, then drops out once the compressor reaches about 70 percent of rated speed. The PTC starter does something similar but without the mechanical contacts. Embraco offers both. The relay type is the one with the spring-loaded contact arm and the coil wound around a ferrite core. For the wiring, it's straightforward if you pay attention to the terminal markings on the relay housing. Terminal 1 (usually the larger spade) connects to the S terminal on the compressor via the start capacitor. Terminal 2 (smaller spade) goes to the R terminal on the compressor directly — no capacitor in this path. The relay body mounts so that its internal contact pin touches the S terminal on the compressor, and the relay's metal mounting bracket grounds to the C terminal through the compressor casing. Actually, let me correct myself. The grounding path isn't always through the casing on Embraco units. Some newer models use a separate ground wire from the relay bracket to the compressor frame stud. I found this on a SHR series where the old relay was mounted directly to a threaded hole and the new one needed an added ground strap. Without it, the unit tripped on ground fault after running for a few hours.

The start capacitor connects between terminal 1 on the relay and the S terminal on the compressor. Its value is usually between 50 and 150 microfarads depending on compressor displacement. Embraco's own spec sheets list the exact value for each model. Don't guess here — I've seen people throw a 100uF capacitor on a compressor that needed 68uF and end up with burnt start windings within a month. The run capacitor, if the unit has one, connects across R and C on the compressor. This is a separate component from the start capacitor and stays in circuit the entire time the compressor runs. Some Embraco configurations don't use a run capacitor at all and rely on the motor's internal design instead. Check the nameplate or the wiring diagram sticker on the compressor body before assuming both capacitors are present. Here's what most people miss when they're looking at an Embraco start relay wiring diagram for the first time. The relay coil doesn't connect to line voltage directly. It's fed through the overload protector, which means if the overload is open, the relay can't pull in even if the coil is good. I spent twenty minutes troubleshooting a dead relay on a chest freezer only to find the thermal cutout inside the overload was open at room temperature. That's rare but it happens, and it'll waste your afternoon if you don't check it.

Another thing that trips people up: the relay contact resistance. New Embraco relays measure less than 0.5 ohms across the main contact when closed. After a few years of arcing, that climbs. If you're diagnosing an intermittent start failure and the relay clicks but the compressor doesn't turn, measure the contact resistance while the relay is energized. Values above 2 ohms mean the contacts are wearing out and the relay needs replacement even if it still clicks audibly. For a practical wiring reference, here's the sequence I follow when replacing a relay on an Embraco compressor. First, unplug the unit and wait five minutes for the capacitors to discharge. Then label each wire with masking tape before disconnecting anything. Embraco colors aren't standardized across product lines — blue might be start on one model and run on another. The labels save you from reconnecting things in the wrong order later. Disconnect the old relay by pulling it straight off the S terminal. Don't wiggle it. The terminal pins are crimped and wiggling widens the socket on the compressor, which causes poor contact and arcing. I've opened up so many compressed with spread terminal sockets from relay removals that went the wrong way. If the pins are stuck, use a small pry bar on the relay housing, not on the compressor terminals.

Install the new relay by pressing it firmly onto the S terminal until the contact pin seats fully. The relay should sit flush against the terminal plate with no gap. If there's a gap, the internal contact isn't touching the S pin properly and the compressor won't get start current. Check this visually before you reconnect anything else. Reconnect the capacitor wires to their labeled positions. The start capacitor goes to terminal 1 on the relay and S on the compressor. The run capacitor (if present) goes across R and C. Double-check each connection with a multimeter before powering up. Continuity from R to C should read the run winding resistance, typically between 1 and 5 ohms on Embraco residential compressors. R to S should read slightly higher due to the series capacitor path. S to C should show the start winding, usually in the 2 to 8 ohm range. If your resistance measurements are open or near zero, the compressor windings are damaged and no amount of relay work will fix it. I had a customer bring me a unit that kept tripping the overload. The relay was new, the capacitors tested good, but the S-to-C reading was 0.3 ohms. Compressor locked up internally. We replaced the compressor and the problem went away immediately.

One edge case that's worth noting: Embraco compressors used in export markets sometimes have different terminal configurations than the domestic versions. I ran into this with a Brazilian-import unit where the terminal layout didn't match any diagram in the service manual. The solution was to trace each wire back to its source on the control board rather than trusting the terminal labels. It took longer but prevented me from connecting the relay backwards. If you need an actual diagram for reference, Embraco's technical documentation is available through their official service portal. The wiring diagrams are model-specific and usually cover 2 to 4 pages per compressor family. Generic diagrams online are often inaccurate for Embraco units specifically — they tend to conflate different manufacturers' terminal arrangements. Stick to the manufacturer documentation when possible. The whole process, from diagnosis to a running compressor, typically takes between 30 and 90 minutes depending on access conditions. Tight spaces behind the fridge add significant time because you're working with limited visibility and small connectors. I've done relay replacements in under 20 minutes on units with exposed terminal boards and over 3 hours on built-in installations where I had to remove the kick plate, the condenser coil cover, and reroute several hoses to reach the compressor.

If your Embraco compressor still won't start after a relay and capacitor replacement, the next thing to check is the control board output. Measure voltage at the compressor terminals with the unit powered on and calling for cooling. You should see 120VAC (or 230VAC depending on market) between L and N on the power feed. If the voltage is present but the compressor doesn't respond, the issue is almost certainly mechanical — seized bearings or a locked rotor. Listen for a hum from the compressor. A steady hum with no rotation means the motor is trying to start but can't turn. I should also mention that some Embraco models use an integrated start component rather than a separate relay and capacitor. These are smaller and mount directly on the terminal plate. The wiring is simpler but the parts are less interchangeable. If you're working on one of these units, make sure you have the exact replacement part number before ordering. The physical size might look identical but the electrical specifications can differ significantly between variants. When in doubt about any connection, take a photo before you disconnect anything. Modern phone cameras capture enough detail to trace every wire back to its origin. I've saved myself from several wrong reconnections this way, especially on units where the factory wiring had been modified by a previous technician.