What causes idle RPM to drop when air conditioner is on?
However, if the IAC is working, then it may be resistance from the AC compressor. This often happens because the AC system leaked out enough refrigerant over the years normally. People let it run without service, then the compressor seizes up ($$).
How much does a new Mercury Grand Marquis cost?
A new, upgraded fan motor and resistor may be required to correct this concern. The average cost for a Mercury Grand Marquis General Diagnosis is between $88 -$111. Learn More Car overheats while at an idle most of the time with the air conditioning on.
What causes rpm to jump back up at idle?
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.
What causes the engine to slow down at idle?
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 happens when engine RPM drops below 800?
However, when the engine RPM drops below the normal range of 800 RPM (for most cars), it is more than likely that you are dealing with an IAC valve problem. In cases where this valve is clogged or is failing, your vehicle will stall instead of slowing to an idle after the release of the throttle.
A new, upgraded fan motor and resistor may be required to correct this concern. The average cost for a Mercury Grand Marquis General Diagnosis is between $88 -$111. Learn More Car overheats while at an idle most of the time with the air conditioning on.
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.
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.