I have a 14 year old Yaris 1.4 D4-D Linea Terra. It has got an interesting phenomena in the last few months: when the engine starts and it reaches the operating temperature, the idle start increasing a bit. It is always increasing when the fan in the passenger area is working. When I turn off the fan, the idle drops to normal. If I turn on the fan again, after a few seconds the idle starts increasing again. I thought the generator causes the problem, so I had it checked with an electrician, but he found nothing. What can cause the problem? Has anybody experienced like that? What can be done?