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The fan will also run when the A/C comprssor is running, along with running to keep the engine cool.
If it is running more than normal there may be a problem with the cooling system and the fan has to run more to keep the temp in the normal range.
If the fan is louder than normal the fan itself may be going bad.
By checking the radiator as I described you can rule out the radiator.
When the engine is at normal operating temperature, shut the engine off and see it the radiator is cold at the bottom. The higher you have to move up the radiator to find heat the worse it is. Be carful of the fan, it can kick on even when the engine is off. If you have one of those non-contact thermometers, they work well to check it.
I took my MPV to a mechanic who checked radiator pressure and it was OK. Then he flushed the radiator and put new coolant. The problem is the same.
I compared my mpv with a friend's mpv and I noticed my right fan stops for a second and then runs slowly whereas my friends mpv the right fan comes to complete stop for few seconds and then works. I also noticed my fan is more noisy compared to his car.
Does that give you any clue?