I have a one question i have owner Tata Indica V2 . my question is when i start car ac rpm flucating up and down and similar pickup also same with rpm. what is the reasion and please give me solution
I suspect you are referring to the apparent dip in idle speed when switching the A/C on and subsequent correction. What actually happens is that the A/C compressor clutch kicks in so that the drivebelt attached to the A/C compressor pulley wheel is then presented with the additional load required to rotate the compressor internals that circulate the refrigerant.
This additional load placed on the engine causes the idle speed to slow down. What then happens is that the engine management software on the ECU detects that the idle speed has dropped and adjusts the idle control valve / throttle flap position accordingly. This then causes the RPM to jump back up again and then settle to a comfortable idle speed.
You see the same thing to a lesser extent when turning on other systems on the car such as the heated rear screen. It's most evident with the A/C compressor as this has is one of the biggest drains on the system in terms of additional equipment.