Yaris idle problem with passenger fan

[sievy]

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?

[FROSTYBALLS]

Moved to the Yaris club.

[mrfixer]

The fan draws in excess of 10A which means it is a considerable electrical load. The engine ECU senses the load and increases the engine idle speed to increase the generator output and ensure that the Battery is not discharged. 

[scannerman]

Is your A\C on? If it is, then turning the fan off will also switch of the A\C. It's not unusual for the engine idle to increase slightly when the A\C pump starts. If it is on, turn it off and see if you have the same result with the fan only.