Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
A/C Signal Circuit Troubleshooting
- Start the engine.
- Turn the blower switch ON.
- Turn the A/C switch ON.
- Check the A/C CLUTCH in the DATA LIST with the HDS.
Does it indicate ON?
- YES - Go to step 5.
- NO - Go to the A/C pressure switch test (see A/C PRESSURE SWITCH CIRCUIT TROUBLESHOOTING .
- Check the A/C system.
Does the A/C system operate?
- YES - The air conditioning system circuit is OK.
- NO - Go to step 6.
- Turn the ignition switch OFF.
- Turn the ignition switch ON (II).
- Activate the A/C CLUTCH in the INSPECTION MENU with the HDS.
Is there a clicking noise from the A/C compressor clutch?
- YES - Do the A/C system test (see A/C SYSTEM TEST ).
- NO - Go to step 9.
- Turn the ignition switch OFF.
- Jump the SCS line with the HDS.
- Disconnect PCM connector B (56P).
- Turn the ignition switch ON (II).
- Momentarily connect PCM connector terminal B11 to body ground with a jumper wire several times.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there a clicking noise from the A/C compressor clutch?
- YES - Update the PCM if it does not have the latest software, or substitute a known-good PCM (see PCM UPDATING AND SUBSTITUTION FOR TESTING ), then recheck. If the symptom/ indication goes away with a known-good PCM, replace the original PCM (see PCM REPLACEMENT ). The air conditioning signal OK.
- NO - Check for poor connections or loose terminals at the A/C clutch relay and the PCM. If they are OK, check for the A/C clutch relay (see POWER RELAY TEST ), and other A/C systems.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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