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DTC codes / Ford codes / P1308

P1308 · FordA/C Clutch Circuit Fault

P1308 on Ford vehicles indicates that the powertrain control module (PCM) has detected a fault in the air conditioning (A/C) clutch control circuit, meaning the electrical path that engages the compressor clutch is not behaving as expected. The PCM monitors the circuit for open circuits, short circuits, and excessive current draw, and it sets this code when the feedback does not match the commanded state. This fault can prevent the A/C compressor from engaging, resulting in no cold air from the vents.

SystemPowertrain
Code typeFord specific
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • The A/C blows warm air or no cold air at all because the compressor clutch never engages.
  • The A/C compressor clutch may engage and disengage rapidly or stay engaged constantly, depending on the type of circuit fault.
  • The check engine light or a dedicated A/C warning light illuminates on the dashboard.
  • The engine may idle roughly or stall when the A/C is turned on if the clutch circuit is shorted and loads the electrical system.
  • Often no symptoms besides the warning light if the fault is intermittent or only affects a feedback signal.
  • The A/C may work intermittently, engaging only on certain days or after the vehicle has been driven for a while.

Common causes, most likely first

  1. A failed A/C compressor clutch coil that has an open winding or shorted turns, which is the most common cause on high-mileage Ford vehicles.
  2. Damaged or corroded wiring and connectors between the PCM and the A/C clutch, including chafed harnesses near the compressor or at the clutch connector.
  3. A faulty A/C clutch relay that has burned contacts or a stuck coil, preventing proper power delivery to the clutch.
  4. A blown fuse or fusible link in the A/C clutch power circuit, often caused by a shorted clutch coil or wiring.
  5. A PCM driver circuit failure inside the PCM, which is less common but can occur if the clutch circuit has been shorted for an extended period.
  6. A seized A/C compressor clutch bearing or mechanical failure that causes excessive current draw and sets the circuit fault.
  7. Poor ground connection at the clutch housing or chassis, leading to erratic clutch operation and a circuit fault.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in the PCM and body control module (BCM) to confirm the fault is isolated to the A/C clutch circuit.
  2. Inspect the A/C clutch relay, fuse, and wiring for obvious damage, corrosion, or loose connections, and test the relay by swapping it with a known-good relay of the same type.
  3. Measure resistance across the A/C clutch coil at the clutch connector; a good coil typically reads between 2 and 5 ohms, while an open or shorted coil will read outside this range.
  4. Check for power and ground at the clutch connector with the A/C commanded on, using a multimeter or test light to confirm the PCM is supplying voltage and the ground path is intact.
  5. Inspect the wiring harness from the PCM to the clutch for chafing, pinched wires, or corrosion, especially near the compressor and along the engine block.
  6. If the coil, wiring, and relay are good, test the PCM driver circuit with a noid light or oscilloscope to confirm the PCM is commanding the clutch on; replace the PCM only if the driver is faulty.
  7. After repairs, clear the code and verify the A/C clutch engages smoothly and the code does not return during a road test with the A/C on.

What Ford technicians check before replacing the PCM

  • A shorted A/C clutch coil can damage the PCM driver circuit over time, so always measure coil resistance before installing a new PCM to avoid repeating the failure.
  • On many Ford models, the A/C clutch relay is shared with other circuits, so a fault in a seemingly unrelated system can cause the relay to behave erratically and set P1308.
  • Intermittent P1308 codes often trace to a chafed wire near the compressor pulley or a corroded connector pin that only loses contact when the engine moves under load.
  • The PCM may set P1308 even when the A/C clutch is mechanically seized and drawing excessive current, so always check for a seized clutch bearing before condemning the electrical circuit.
  • Some Ford vehicles use a variable-displacement A/C compressor without a traditional clutch, and P1308 may indicate a fault in the control valve circuit rather than a clutch coil, so confirm the system type before testing.

Can I keep driving with P1308?

You can usually drive the vehicle with P1308, but the A/C will not function and the compressor clutch may cycle erratically, which can cause engine idle fluctuations. Avoid using the A/C until the fault is repaired, and if the engine stalls or idles poorly when the A/C is turned on, have the vehicle inspected promptly to prevent further electrical damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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