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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Climate Control REST function

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      11-17-2012, 08:43 PM   #23

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i have a 2008 335xi i dont see this button anywhere. do i have it? thanks
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      11-18-2012, 11:21 AM   #24
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The REST function incorporates an auxiliary coolant circulation pump located in the engine bay close to the passenger wheel well, when you hit the rest button and the appropriate parameters have been met this powers up and circulates coolant through the heater coil in the cabin, providing residual heat from the engine/coolant until it drops too cool or the battery voltage drops too low therefore I think simply coding the car and replacing "ALL" with the rest function won't be possible as you'll be missing the circulation pump!
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      11-18-2012, 11:39 AM   #25
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Probably in the minority here but much prefer the button functioning as "All" in my LCI. I had the Rest function in my old 330d and never used it. Much prefer the All function of keeping the temps in synch.

Interestingly the new F30 I had the other week had neither function and looks like it does Max air con. Cost saving again I suppose...........

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      11-18-2012, 03:48 PM   #26
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As this is now going off topic, I'll chuck in my 2p

Does anyone actally use the dual zone AC? I set both sides to how warm or cool I want the car - always the same temperature. If the passenger doesn't llike it, they can close the vents on their side.

AFAIK there is only one cabin temperature sensor, which is in the middle of the console - so I genuinely don't know how it can try to keep 2 temperatures.
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      11-19-2012, 06:04 AM   #27
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Originally Posted by parapaul View Post
AFAIK there is only one cabin temperature sensor, which is in the middle of the console - so I genuinely don't know how it can try to keep 2 temperatures.
BMW Data:

The temperature inside the vehicle is controlled by means of a master controller.

Control is based on the nominal values set and the calculated actual value (the nominal values are set with 2 temperature selector knobs. The actual value is calculated from the temperatures measured by the interior temperature sensor and the footwell temperature sensor).

The lead parameter is calculated from the comparison between the actual value for the interior temperature and the corrected nominal value (calculated from temperature request, interior temperature and ambient temperature). Compared to the set specification, the interior temperature is raised in the cold so that a comfortable level is achieved even at negative temperatures, despite the temperature setting being unchanged.

The ambient temperature is transmitted to the IHKA control unit via the K-CAN.

The separate temperature setting for the driver's side and the front-passenger side makes 2 mixer flaps necessary.
So it appears to use the two temperature requests, two sensors and corrected values. Adjusting via the two (sided) mixer flaps.

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      11-23-2012, 04:40 AM   #28
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I may be wrong, but i have a pre lci so cant actually check. I remember reading in a different thread that if you hold the ALL button for a few seconds it activastes the REST function.

Those of you wih lci models may want to try. Hope it helps
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