Fans not working when car at IDLE
 

Are you talking about the electric fans for radiator cooling?

Yes, it is absolutely normal. Fans provide additional cooling for the radiator when it is needed. When you turn on AC, they start up automatically to provide air flow to the AC condenser that sits inline with the radiator. All modern cars do just that.

I think at least 1 fan must be working to cool the engine !. when ignition is ON and the engine is working. there no fan is working. but when i turn the AC ON both fan start working. i think atleast 1 fan work to cool the engine.

This is my first RX, but typically the fan/fans start as needed to cool the radiator. If your running down the highway both fans are off, if your in traffic both are on.

It is absolutely normal to have no fans working with ac off until the engine reaches a certain temp, then at least one of the fans will kick in. If your temp gauge is past the mid point, and no fan kicks in, then you may have a problem.

This is normal, the fan does not come on until a pre determined temperature of the coolant is reached, at which time the computer module starts the fan or fans, unless the a/c is turn on which starts the fans immediately.
The fans on my Z06 doesn't start until the coolant reaches 230 degrees! or immediately if the a/c is turned on.