The AC relay is located in the engine bay’s under-hood fuse/relay box on the driver’s side, and it’s labeled “A/C” on the lid diagram. If the compressor isn’t engaging, this relay is one of the first components to check.
Location and identification
In a 2013 Honda Civic (9th generation), the A/C compressor clutch relay is housed in the under-hood fuse/relay box inside the engine compartment. The box sits on the driver’s side of the engine bay near the battery, and the lid’s diagram identifies the A/C relay. If your model’s diagram looks different, consult the owner’s manual or the service diagram on the fuse box cover for the exact label.
Under-hood fuse/relay box
Follow these steps to locate the A/C relay inside the engine bay fuse box.
- Open the hood and find the rectangular fuse/relay box in the engine compartment, typically on the driver’s side near the battery or strut tower.
- Unclip and lift the box lid to view the schematic on the underside.
- Look for a relay labeled "A/C" or "AC" in the diagram; this is the A/C compressor clutch relay.
- Confirm the relay’s position by tracing the wiring harness that goes to the A/C compressor clutch.
- Handle the relay carefully to avoid bending pins; if you need to remove it, depress the clip and pull straight out.
The A/C relay is usually one of several relays in the box; the lid’s diagram will show its exact location. If you don’t see an A/C label, consult the vehicle’s manual or the diagram sticker on the nearby fuse box cover.
Testing and replacement
If you’re diagnosing air-conditioning performance or a non-starting AC compressor, you can test or swap the relay to verify it’s faulty. Use these steps carefully.
Swapping with a known-good relay
- Find another relay in the same fuse box with a matching pin configuration (often a horn, fuel pump, or headlight relay).
- Power off the car and disconnect the battery negative terminal if you’ll be handling relays.
- Swap the A/C relay with the identical spare relay.
- Start the car and run the AC to see if the problem follows the relay.
If the AC starts functioning after swapping, the original relay is defective and should be replaced. If the problem persists, the issue lies elsewhere in the AC system or wiring.
Using a multimeter and visual inspection
- With the battery connected, visually inspect the relay pins for burn marks, corrosion, or looseness.
- To test with a multimeter, remove the relay and measure the coil resistance across the coil terminals (check the service manual for the correct pins and expected range).
- Test for continuity between common and normally open contacts when the coil is energized to confirm proper switching behavior (you’ll need a power source to energize the coil for this test).
Note that testing procedures vary by model; refer to Honda’s service manual for exact pinouts and resistance specifications. If you’re unsure, have a professional perform the test to avoid electrical damage.
Additional considerations and safety
Always take safety precautions when working around the vehicle’s electrical system. Disconnect the negative battery terminal before removing relays or fuses to reduce the risk of short circuits. If you’re not confident, consider taking the Civic to a qualified technician or Honda service center. The A/C system also involves refrigerant handling, so any service beyond electrical relays should be performed by professionals with proper equipment.
Summary
For a 2013 Honda Civic, the A/C compressor clutch relay is located in the engine-compartment under-hood fuse/relay box on the driver’s side, labeled A/C on the lid diagram. Confirm the location with the fuse box diagram, and diagnose by swapping with a known-good relay or testing with a multimeter, following safety guidelines. If in doubt, consult the owner’s manual or a professional technician.