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stan
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a/c below 3 degrees

does the following mean that the a/c doesnt work below 3 dgrees..

taken from rave.

Compressor Control
The compressor is engaged by pressing either the automatic mode switch, defrost switch, A/C switch or maximum A/C switch. To prevent a dip in engine speed when the engine is at idle, a time delay of approximately 0.5 second is built into the compressor engagement process. The time delay allows the ECM to increase throttle angle and fuelling in anticipation of the additional load on the engine when the compressor engages.
When it receives an input to engage the compressor, the ATC ECU sends a message to the ECM, via the K bus,instrument pack and CAN bus, to advise that it wants to engage the compressor. Provided there are no engine management problems, the ECM responds by increasing throttle angle and fuelling and sending a message granting the request to the ATC ECU over the CAN bus, instrument pack and K bus. When it receives the grant message, the ATC ECU energises the compressor clutch provided the following conditions exist:
l Engine speed is more than 400 rev/min
l Evaporator temperature is more than 3 °C (37 °F)
l The refrigerant pressure is within limits
l Battery voltage is less than 16 V
l The blower is running
l There are no faults detected by the ATC ECU
The compressor remains engaged until selected off or the required conditions no longer exist. If the evaporator temperature decreases to approximately 2 °C (36 °F) the compressor is disengaged, then re-engaged when the evaporator temperature increases to more than 3 °C (37 °F) again. If battery voltage exceeds 16 V for more than 5 seconds the compressor is disengaged, then re-engaged when voltage decreases to less than 15.8 V.
The compressor can also be disengaged by the ECM changing the grant message to a negative value or outputting a hardwired signal direct to the ATC ECU. Changing the grant message involves a time delay of up to 4 seconds before the ATC ECU de-energises the compressor clutch. The time delay allows the ECM to decrease throttle angle and fuelling, in anticipation of the reduction in engine load when the compressor disengages, to prevent a sudden increase in engine speed if the engine is at idle. The hardwired signal is used to obtain instant disengagement of the compressor to ensure maximum acceleration when accelerator pedal demand suddenly goes from no load to full load.
When this occurs the ECM sends a 12 V signal on a hardwired connection direct to the ATC ECU. When it receives the signal the ATC ECU immediately de-energises the compressor clutch.

Post #44858 6th Jan 2011 12:42pm
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JOKER



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And that Gentlemen is how to complete a Moon Landing ............. Laughing

Exclamation Exclamation Exclamation Exclamation

Post #44859 6th Jan 2011 12:47pm
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stan
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Rolling with laughter ...it does look like that mick.... Laughing

Post #44861 6th Jan 2011 12:49pm
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comports



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Blimey Charlie - Wot did he say..? Was that a Yes or No then..?? Ash
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Post #44871 6th Jan 2011 1:17pm
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dan_uk_1984



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United Kingdom 2006 Range Rover Supercharged 4.2 SC V8 Tonga Green

When the evaporator is below 3 degrees - This is the bit inside the car, it will always be above 3C except when you first start the car if its super old outside. As soon as the interior warms to above 3C then the AC pump will run.

The reason there is this 3C switch is that otherwise the evaporator would turn into a block of ice.

So YES, your A/C will still cycle on and off regardless of what temperature it is OUTSIDE the car. 

Post #44872 6th Jan 2011 1:53pm
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stan
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i was hoping you would clarify that dan ... Thumbs Up

Post #44876 6th Jan 2011 2:03pm
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comports



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United Kingdom 2016 Range Rover Autobiography SDV8 Mariana Black

cool (excuse the pun) - looks like we have a safe landing at last. Laughing Ash
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2016 SDV8 AB

Post #44897 6th Jan 2011 4:21pm
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