aircon question

deian · Post by **deian** » 22 Jul 2006, 16:09

recently in this hot weather (wednesday notecably hot) i was coming back from work at 4:30, it was baking so i put my aircon on, and few minutes into the drive i heard this massive whirring sound which i thought were the heavy trucks building a new supermarket close by where i stopped by shops waiting for my workmate to come back. so i switch it off and on, to see if the noise stops, of course the fans took time to come off and on with the air con switch, so i thought nothing of it, so all on the way home the noise was still there, i guess it was the high speed of the fans! Insanely high speed and helicopter like!

Anyway, my question is, does the fact that the fans run on high speed with aircon on make the aircon pump work harder therefore zapping engine power more than if the aircon was on on a cooler day with the fans running only on low speed?

thanks

Kowalski · Post by **Kowalski** » 22 Jul 2006, 16:21

There is a pressure switch on the Xantia air con system (on the receiver / dryer) and if the pressure gets too high in the system it turns the fans up to full speed (panic mode). If it was a hot day, you had a big load on the air con and the car was stationary (or driving slowly / in start stop traffic) it could happen.

If the fans hadn't gone into full speed, the condenser would be hot and the discharge pressure on the compressor would he high, i.e. it would take a more horsepower to run the compressor if the condenser is too hot. If the discharge pressure got too high, the clutch on your compressor would not be able to cope with the horsepower required to pump refrigerant and it would slip, either the clutch or the belt neither of which is good.

To answer your question, yes the fans use horsepower but if they don't cool the condensor the compressor will use more horsepower and ultimately something would break or wear out.

deian · Post by **deian** » 22 Jul 2006, 16:25

it was quite noticeable difference, especially pulling up hill, i always though a 2.1td wouldn't feel air con at all compared to maybe a 1.8 mondeo which were apparently bad and often stalled. i also feel i could do with the belt changed too, i guess that can't help much either

thanks for the prompt reply

np · Post by np » 22 Jul 2006, 16:54

I too notice quite a difference when the air con is on.It seems to sap quite a bit of power on mine.

NiSk · Post by **NiSk** » 22 Jul 2006, 18:01

The A/C on the 2.1 TD12 saps between 7-10 hp. So yes, it is noticable - on my old XM with the same engine, I often switched off the A/C if I wanted to perform a quick overtaking manouver.

//NiSk

deian · Post by **deian** » 22 Jul 2006, 18:16

oh dear thats quite a bit, problem is with switching it off for overtaking is it takes time to disengage?? am i right? or is it just the fans that take time to realise the a/c is off?

SimonM · Post by **SimonM** » 22 Jul 2006, 18:37

deian wrote:oh dear thats quite a bit, problem is with switching it off for overtaking is it takes time to disengage?? am i right? or is it just the fans that take time to realise the a/c is off?

I used to have an S60 D5, this would automatically disengage the A/C under full throttle conditions such as overtaking, didn't really notice the difference though as it had 163HP aqnd 340NM of torque

np · Post by np » 22 Jul 2006, 23:01

When towing our caravan,having the A/C on makes a big difference,not only in performance,but also engine running temp.It does seem to put more strain on the engine with the A/C on.Its been like this since i got the car.
On the other hand,my Dad`s(soon to be mine

)`03 406 HDI,having the A/C on or off makes absolutly no difference to performance at all.Or running temp.You bearly feel the compressor kick in.