Air recirculate turning itself off?

[biffa75]

Hi all,

I've noticed on the wife's 75 classic se (on atc) with the air con on and recirculate on, the reciculate turns itself off after a few minutes? You can turn it back on to recirculate again but turns itself back off again after a few minutes.

Any ideas why this is happening?

[R75800sd1]

As far as I know they are set up to do that, so they don't recirculate stale air for long. All mine do it.

[SD1too]

I don't believe that is a fault Robert. You'll appreciate that some fresh air has to be introduced to the cabin. I think that one of the manuals says that windows would become foggy if the air was recirculated permanently but I'd have to check.

Simon

[daveo138]

I was a bit concerned that my recirculate light was ON when I hadn't pressed the button.

On reading the handbook, it seems that it comes on as soon as you start the engine, then switches off after 4 minutes, for the reasons stated above.

[biffa75]

Thank you for the replies, makes perfect sense as to why it switches itself off to prevent the windows fogging and stale air etc. I guess I've never used the Aircon in the car for long enough to notice until now.

Thanks again 😁

Rob

[bl52krz]

If you are on a journey, and you can see or worse still, smell something, you can hit the recirc button to stop smoke or farmyard smells permeating the inside. You can also use it in the winter, for a short time before the windows steam up, so that the interior warms up quickly.

[Kaloz]

In the recent hot weather my air conditioning has remained in recirculation while in Auto mode.
My handbook says “ the feature [recirculation] also significantly influences the dehumidifying and cooling performance of the air conditioning system. Therefore, in Auto mode, air recirculation is controlled automatically to enable the air conditioning system to achieve its optimum performance “ Page 54
I assumed the air conditioning system stayed in recirculation until the air in the car had cooled, when the system then changed to draw in air from outside.
Is this incorrect ?

Nigel

[Kaloz]

I’ve also noticed that when in Auto mode outside air will be drawn in through the air conditioning system until the ambient air reaches around 23c, after which Auto mode switches to recirculation
Nigel

[SD1too]

Originally Posted by Kaloz

I assumed the air conditioning system stayed in recirculation until the air in the car had cooled, when the system then changed to draw in air from outside.
Is this incorrect ?

Hi Nigel,

It remains a mystery under what conditions the system switches to and from recirculation mode. This is a question for the software designers. It appears that, rather crudely, when the interior temperature is above a certain threshold recirculation is activated. This is actually nonsensical as the system attempts to cool air which is hotter than that outside the car!

The best way around this is to take manual control. In extreme heat the "lazy venting" feature can be used when you first approach your mobile greenhouse (this opens all the windows and sunroof with a single turn of the key and can be activated by T4). When the engine is started with air conditioning on, cancel the automatic recirculation setting and select both temperature controls to 'LO' to produce the coolest possible air. Manually close the sunroof and front windows but leave the rear glasses lowered by about three inches to help the blower assisted expulsion of hot air. Close the rear windows as soon as it is comfortable to do so and when the air conditioning is producing moderately cool air, manually select recirculation mode. Drive off without delay as road speed will increase the cooling effect at the condenser. When you have control over the temperature inside the car you can return to 'Auto' mode and select your chosen temperature above the 'LO' setting.

This is broadly the advice given in my SD1 owner's handbook published in the 1980s and it still holds true today.

Simon

[Vantheman]

Am I right in thinking that if you press and hold the recirc button for a couple of seconds it beeps and stays in recirc mode? I'm sure I've read this but can't remember if I've tried it myself.