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.
Chart C-10, A/C Compressor Clutch Circuit Diagnosis
Turning on A/C supplies battery voltage to A/C compressor clutch relay through circuit No. 59 (PCM terminal E12). After a momentary delay, Powertrain Control Module (PCM) will ground circuit No. 459, closing A/C compressor clutch relay and engaging A/C compressor clutch.
PCM control of A/C compressor clutch improves idle quality by delaying A/C clutch engagement until idle speed is increased and releasing A/C clutch when idle speed is too low. PCM smooths cycling of A/C compressor by providing additional fuel the instant A/C clutch is applied.
- Checks if low refrigerant is causing an inoperative A/C system.
- This tests for a faulty A/C compressor clutch relay or a faulty high or low pressure cut-out switch.
NO RELATED
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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.