Hello,
I've been trying to track down this issue for a while now and I'm stumped. I have a 2010 V6 Accord and every time the AC is on, the engine gets over cooled. Enough that the gauge goes down down to 1/4. Before I noticed that the AC was causing it to go down, I thought I had a stuck thermostat so I replaced it with an OEM one. That didn't fix the issue, so I then changed the ECT sensor. Still that didn't fix the issue either. I search and search and no one seems to have the same problem.

Now that I know it's related to the AC, I noticed that every time the AC is on, both condenser and radiator fans are blowing at full speed and are always on until I turn of the AC. That differs from what I've seen on the forums and also on my other accord that has the K24 engine. In that accord, the radiator fan cycles on/off every 15 or so seconds.

My question is, what controls the fan to cycle on/off every 15 seconds? Is there anything else that causes the engine to over cool itself?

Thanks in advance!

 

The ECM/PCM detects that the A/C is ON through an input from the A/C Pressure Sensor.

• At normal A/C refrigerant pressure, both cooling fans operate at low speed (unless the engine coolant temperature exceed 206 degrees F). The ECM/PCM cycles the A/C compressor clutch based on cooling demand.
• At high A/C refrigerant pressure (rises above 1520 kPa (221 psi)), both cooling fans operate at high speed. The ECM/PCM cycles the A/C compressor clutch based on cooling demand.
• Abnormally high or low A/C refrigerant pressure, the ECM/PCM will disengage the A/C compressor clutch.

 

Could be a faulty A/C Pressure Sensor or a Faulty Temp Sensor. It seems like for some reason both your A/C condenser fan & radiator fan are running. When A/C is on the fans should both cycle @ normal operating temp. If both fans are running then it's going to cool the radiator and coolant down too much.