Thank you for all the replies to my previous question.
A final thought, if you need to run your air con all the time to keep it working properly and avoid expensive repairs, why do manufactures provide you with the facility to switch it off?
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Because it increases fuel consumption and there maybe times when you don't actually want it on. Still, I do think certain Yank Tanks have it permanently on - If I recall correctly early Volvo 760s had no switch and the AC pump was permanently on. Still, those have large engines unaffected by the load of a refrigerant pump - I remember a girl I know from Spain who had a 1.6 Suzuki Vitara and said she had to turn the aircon off to overtake anything.
I think if you used it every day (say to clear the windscreen in winter and to cool the car when weather warmer) you should have no trouble with it - it's the people who don't bother to use it all winter and then wonder why nothing happens 8 months later on a hot day (seals have dried up and gas escaped!).
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I've had the dubious pleasure of driving a Daihatsu 996cc car with aircon. I'm sure the thing 'steals' 25% of the engine power output!
Turn it on, and it feels like three blokes have just jumped into the back seat!
It seems some manufacturers don't think of logic when they add 'extras'...
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As I pointed out in an earlier thread, Fords handbook for the Fiesta buries the information that the a/c needs to be used for at least 30mins per month in a footnote near the end of the book. It also omits to mention the reason it needs to be used. How many owners of what is basically just a runabout ever read any of the handbook, let alone search for technical information? There must be a lot of Fiestas out there with seriously sh****d air-con systems by the end of every winter.
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Although my system will switch itself back on every time you start the engine I have noticed that it automatically switches itself off when the outside temp. drops below zero. Presumably to prevent icing.
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A/C only takes power when it is actually having to work, a bit like the alternator for instance. Therefore in winter, when the heat load is low, it does hardly anything (obviously), therefore uses very little power.
Compressors are rated at about 28,000 btu, therefore can take about 12 hp at full chat. Bear in mind that a small engined car only develops a peak of 60 hp, much less at lower revs, it will give the engine something to do, but again, only when it is having to work hard. You don't get something for nothing in this world.
As regards the 'turn-off to go uphill' story. It always makes amusing reading, but is sadly not true. Virtually everycar monitors the throttle position sensor, and if it see's a large throttle movement it shuts the a/c down. They also now monitor the power steering pressure, so if hard lock is required, it will again cut the a/c, or increase the idle speed to further compensate.
It is true that some cars run the compressor all the time, just like you run the alternator or PAS pump, even when running during the day in a straight line!
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talking about power sterring
having recently been in an engine cut situation
i was surprized
i) how soon the power assistance failed (why isnt there some reserve like there is in the brakes?)
ii) how very heavy it was to steer - if it had been the misus driving im sure she wouldnt have been able to steer and would have crashed
just wondering
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Power steering by the way in which it works requires constant pressure and movement of oil from the pump.
You think that was bad, you want to try driving an old Yank Tank when over 2 tons of metal loses the ability to be steered or stopped!
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It may well be true that for most cars now the a/c doesn't make a lot of difference. That was certainly true for my R-reg 1.25 Zetec Fiesta. However, in the mid-80s I hired what trned out to be an American Motors-badged Renault 11 in the States. When the a/c was turned on there was a marked 10mph drop in speed when under any stress such as climbing a long uphill freeway. For overtaking on normal roads I had to turn it off. Still got a ticket for exceeding the 55mph limit though.
David Millar
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Many cars these days default the a/c system ON from start-up. Mercedes Benz is one such example.
Personally, I use my a/c all year round - we are in the a/c repair business (like Dave N) and see the result of unused systems.
This will be a real problem in 5-8 years time (probably sooner) when all the cars equipped with a/c when it was 'trendy' to have it, come into the hands of garages and owners with knackered a/c systems. Are people prepared to pay large sums of money to repair these sometimes exotic systems?
David
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can someone explain to me why it is that Honda has fitted air con to mainstream models since the mid-1970s and (on the whole) as long as the system gets an occasional recharge it just goes on working, while air con systems fitted to other makes seem to reduce fuel consumption, give major problems or just smell horrible! is there a lesson here? incidentally - hi david! hope you're well and still making a living hammering rovers back together!
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