BECM - prophylactic

JohnP38 said:

Many vehicles when you switch on the "defog" mode, switch on the A/C as well to dry the air.

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Wiganerdan said:

On your Range Rover the air con is always on unless you physically turn it off with the air con off button. It's the fastest way of clearing steamed up/fogged up windows. Air conditioning does what it says, it conditions the air. It dehumidifies it, and by virtue of the fact it fridges it as well it kills a lot of bacteria, though these will grow on your evaporator. It works with the heaters on any temp and will help to keep the inside of your car dry. As for the economy side of things, on a car as thirsty as a 4.6 p38 it makes pretty much naff all difference, especially as it's a modern day system that cycles the compressor on and off. There always used to be a thing for removing the belt on cars to save fuel, but seeing as with the compresor off it's just an idler pulley that makes sod all difference as well.
A lot of big engined cars like V12 jags, Rolls Ryce and Bentley etc also rely on the air conditioning for fuel cooling. Disconnect the air con, no fuel cooling leads to a massive increase in evaporative losses and actually costs you more than if you where using the system./
Having worked in the prestige vehicle sector all my working life it does grind a little when people buy a big luxury car with a big engine and then gripe about the amount of fuel it uses. Changing your driving style and keeping things maintained is far the biggest fuel saver.

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Wiganerdan said:

On your Range Rover the air con is always on unless you physically turn it off with the air con off button. It's the fastest way of clearing steamed up/fogged up windows. Air conditioning does what it says, it conditions the air. It dehumidifies it, and by virtue of the fact it fridges it as well it kills a lot of bacteria, though these will grow on your evaporator. It works with the heaters on any temp and will help to keep the inside of your car dry. As for the economy side of things, on a car as thirsty as a 4.6 p38 it makes pretty much naff all difference, especially as it's a modern day system that cycles the compressor on and off. There always used to be a thing for removing the belt on cars to save fuel, but seeing as with the compresor off it's just an idler pulley that makes sod all difference as well.
A lot of big engined cars like V12 jags, Rolls Ryce and Bentley etc also rely on the air conditioning for fuel cooling. Disconnect the air con, no fuel cooling leads to a massive increase in evaporative losses and actually costs you more than if you where using the system./
Having worked in the prestige vehicle sector all my working life it does grind a little when people buy a big luxury car with a big engine and then gripe about the amount of fuel it uses. Changing your driving style and keeping things maintained is far the biggest fuel saver.

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Wiganerdan said:

No, it's on when you select hot. Temperature settings have nothing to do with it. The Evaporator temperature senesor is only there to stop the evaporator freezing up by turning off the compressor when a pre determined temp is reached. In the old days it used to be done by a thing called a ranco stat. Then you had variable suction throttling valves that could adjust the amount of fridge required and nowadays it's done electronically by a variable resistance temp sensor and cycling the compressor through an ecu. The other temperature sensor which on other systems is normally known as a 44 degree switch is there to hold off the fans until the heater matrix temp is at a certain point purely from a comfort point of view so when you climb in your car in arctic conditions you don't get a face full of frosty air.
Temperature settings have absolutely sod all to do with it. It should run all the time, from first start to switch off regardless of anything.
If memory serves me correctly, the old range rovers didn't have air conditioning, they simply had a fridge unit under the passenger side dash feeding a row of vents. That is a fridge system, not an aircon system and purely used for cooling.
Climate control with air conditioning is what is fitted to a Range Rover and that is exactly what it does unless you don't want it to, which is why they give you the aircon off switch.

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Wiganerdan said:

Because it is a dehumidifier. This is somoething people don't seem to be able to get their head round. Stop thinking of it just as a fridge. It is a dehumidifier/air purifier. It just does this by fridging the air. And believe it or not, it allows the matrix to heat the air faster, bit like the old hot water freezes faster than cold water but in reverse. All to do with the physics of temperature gradients.

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defender300td1 said:

Oic now regersted bit slow but got there

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Wiganerdan said:

Because it is a dehumidifier. This is something people don't seem to be able to get their head round. Stop thinking of it just as a fridge. It is a dehumidifier/air purifier. It just does this by fridging the air. And believe it or not, it allows the matrix to heat the air faster, bit like the old hot water freezes faster than cold water but in reverse. All to do with the physics of temperature gradients.

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Wiganerdan said:

Because it is a dehumidifier. This is something people don't seem to be able to get their head round. Stop thinking of it just as a fridge. It is a dehumidifier/air purifier. It just does this by fridging the air. And believe it or not, it allows the matrix to heat the air faster, bit like the old hot water freezes faster than cold water but in reverse. All to do with the physics of temperature gradients.

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Wiganerdan said:

Errr you could say I know a thing or two about it.

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