Vehicle: 2011 Ford Taurus FWD V6-3.5L
Problem: The vehicle owner brought the vehicle to the shop because sometimes the water temperature gauge read too high, especially with the A/C on.
Case Details: The technician verified that the engine did not overheat with the A/C off, only when the A/C was on. He checked the cooling system – it was full of coolant and had no leaks. He checked all related fuses – each had battery voltage and were not open or missing.
He connected a scan tool and found no diagnostic trouble codes. He also noted that when the radiator cooling fan was operating, the PCM variable fan control PID showed 65% at idle, and changed to 100% after three minutes of idling with the A/C on. One minute later though, the variable fan control PID changed to 0% and the fan shut off.
The technician inspected the wiring harness and connectors but found no problems.
Confirmed Repair: He replaced the cooling fan assembly, which came with the variable fan control module. After the repairs, the cooling fan operated normally and the engine no longer overheated with the A/C on. Problem fixed!