Subaru Forrester A/C Quits After Engine Warms Up
Oct. 01 2023
Oct. 01 2023

Vehicle: 2014 Subaru Forester, F4-2.5L DOHC, Automatic Transmission/Transaxle

Mileage: 145,659

Problem: This Forrester was in the shop because the air conditioning would stop working after the engine got up to operating temperature. The customer stated that if he let the engine cool off for a bit, the A/C worked fine until the engine heated up again.

Case Details: The technician verified that the refrigerant charge was correct. Connecting a scan tool, he found no diagnostic trouble codes (DTCs) in any modules. At this point, a call went out to ALLDATA Tech-Assist.

The Tech-Assist consultant recommended monitoring the engine coolant temperature (ECT) sensor PID when the A/C stops working. NOTE: If the powertrain control module (PCM) thinks the engine is overheating, it will shut off the A/C. The problem could be that the engine is overheating or a defective ECT sensor is sending a false overheat signal to the PCM.

If the engine temperature was normal, the consultant advised checking for power at the compressor clutch as soon as the A/C quit. If power was still present, the clutch coil may have an intermittent open or the clutch air gap clearance may be too large. If power was not present, the technician should start inspecting the wiring and connectors.

The technician checked for the overheating condition as advised. The engine was not overheating, and the ECT sensor was good. Next, he checked for power to the A/C clutch when the A/C quit. He noticed that there was still power to the clutch, so it tapped lightly on the pulley. The clutch engaged. The clutch was worn out and the air gap was too large.

Confirmed Repair: The technician replaced the compressor with the clutch, charged the system and ran the A/C in the shop and on the road. The A/C worked flawlessly. Fixed!

The ALLDATA Tech-Assist team fields cases like this every day. See how Tech-Assist can help your shop save time and money with on-call diagnostic support from ASE-certified Master Technicians. More Tech Tips 

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