I own a Lexus RX330, 2005.

My engine cooling fans are switching on/off all the time when A/C is on. It goes like this: 5-10 sec on, 5-10 sec off and so on. Engine temperature (measured by a scanner - 170-190F / 80-90C). It does not happen when A/C is off.

Is it normal?

The problem is when the fans are on, there is an additional engine load (CALC load), so the load changes all the time (at idle - from 17-18% to 20-24%) with a period 5-10 sec. I suspect the periods should be much longer.

this all normal while the vehicle is standing still with the ac on.
once you are driving at higher speeds the air coming through the grill takes over and the fans go back to normal cycle.
In my honda as soon as you turn on the ac- the engine fan turns on no matter the temperature of the coolant..

I like that better,the first time I ever noticed cooling fans cycling with the A/C compressor was on a 1990 Plymouth Acclaim. And I thought how stupid is that?

lol...you see how loud that honda sounds when they turn on.

Probably about the same as my wife`s 06 C-280. Sounds like a Tractor Semi when the A/C is on .