I noticed that when using my air conditioning the note of my engine really changes, it gets really deep, and the usual whine that springs up a 3k revs does not happen, at the red line theres a real noticable chane in the noise, and i even notice a reluctance to Kick down when it's on?

any ideas?

Yeah, alternator will be working harder, so revs will increase/power reduced...

Rob.

Alternator??

Air-conditioning compressor more like. Not even sure it shares a belt with the alternator, but if it does, it would be altering the tension in the belt, and potentially changing the load on the alternator pulley, if that's what normally makes the whine.

Air-conditioning is quite a power drain on a small engine. Even on my 1.8T, I lose about 1.5mpg with it on - and being a cheapskate, I normally run with the climatronic in ECON mode.

HTH.

Isn't the air con compressor powered by electricity...which comes from the alternator? :confused:

Rob.

No, it's powered by a rubber belt, which comes off the engine pulley, just like the alternator.

Oh...right...so surely that means it's running the compressor even when the air con is switched off?

Rob.

Not if the compressor has a clutch or in this case an electro-magnetic coupling.

Which they mostly do. That's the only part that's operated by electricity - a solenoid engages the clutch and instead of just the pulley whirring round, the compressor springs into life...

Well, I never knew that...

Still think my idea would be simpler though...

Rob.

Beans.

= Open windows

IIRC an American (has to be really) did tests. Not sure how accurate, but crusie control on the roads out there must be fairly static. Basically it's the traditional wndows down ac off and windows up ac on..both about the same due to drag and engine load. Personally ice cold, then windows open to warm up, then ac....

notice a reluctance to Kick down when it's on?

I always thought the ECU cut power to the air con under hard acceleration, but maybe that was something unique to the Scooby? Anyone know? FWIW, I don't notice any difference in performance running with air con on or off so I just leave it running all the time

Chris

Yeah' date=' alternator will be working harder, so revs will increase/power reduced...

Rob.[/quote']

Hence the reluctance to kick down

If I remember rightly, the compressor pump on my 'old' Focus was something like a 3/4hp pump. I used the air con a lot of the time and it made absolutely no difference to fuel consumption that I could notice. On the Octavia, again I don't notice any real difference in comsumption.

As had been said above, the compressors do engage/disengage. You can normally hear them engage if you have the window down.

As for not using the air con, I believe they recommend at least 15 minutes uage every week to stop the system drying out.

Andy

My aircon is super cold but you do hear a drop in the egine tone in idle.

But as I idle at 1750rpm, theres a few to go round to all the components that need it