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Are you using it properly? On my petrol 2 litre when the climate control is on I have no control of the fan setting.- i.e. if I swith on the CC and then try to set the fan, the CC switches off.
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He's using it in manual mode.
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when you select Lo the climate control is turned off anyway. It should just be cooooooold
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TourVanMan TM < Ex RF >
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Vent temp should be around 5 degc at 1500rpm and mid fan speed. Measure and report back.
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It took me a while to find a suiable mercury lab-style thermometer, however I have done this test for 5 mins or so and it does just get to 5 degrees with the thermometer stuck into the fascia vent with the fan on full at abiut 1500 revs.
Thanks for the info.
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Silly question but you don't have the "Economy" switch on do you?
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Can you really hope for 5C from the vents? Surely the external ambient has got an effect and all you can hope for is a certain temperature drop?
I'm interested as I have a Passat with a presumably similar climate control system.A couple of years ago I measured around 12C from my vents ,using a thermocouple, on a hot day.
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I wasna fu but just had plenty.
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Can you really hope for 5C from the vents? Surely the external ambient has got an effect and all you can hope for is a certain temperature drop?
Yes. The system has an over capacity, otherwise it would never get the temperature down in the first place, let alone keep it there. Don't forget, a car system can use about 10-12KW of power, that's a lot of cooling power. Certainly a lot more than a 4 bedroom house would require for a/c.
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A belt driven compressor that handles 10-12Kw I don't think so. Where did you get those figures from. I have seen 2-4KW mentioned before but 12KW thats 15HP. No way. Interesting though. Regards Peter
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A belt driven compressor that handles 10-12Kw I don't think so. Where did you get those figures from. I have seen 2-4KW mentioned before but 12KW thats 15HP. No way. Interesting though. Regards Peter
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Sorry, should have said 10-12HP, not KW.
I suggest you look at the Sanden web site. Their graph shows power consumption of 8HP at 4000rpm. It's almost a straight line from zero rpm to 4000, therefore at 6000rpm my simple mathematics tells me it's 12HP. In fact, most compresors are geared to run fastser than engine speed, so could potentially run to 7000rpm.
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. It's almost a straight line from zero rpm to 4000, therefore at 6000rpm my simple mathematics tells me it's 12HP. In fact, most compresors are geared to run fastser than engine speed, so could potentially run to 7000rpm.
The compressor disengages at 4000rpm, that's why it only goes up that far. It also disengages at WOT regardless of RPM in most applications. What's more, the compressors cycle in and out by control of a thermocouple or sensor in the evaporator, so it's very difficult to calculate the power used over a journey with all the variables there are.
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The compressor doesn't disengage at 4000rpm. It will disengage on WOT, but the ecu looks for a big movement of the TPS, not it's final position (alhough some don't have a WOT cutout at all). No-one is measuring the total power useage, as you're quite correct the compressor does come on and off, or varies it's output depending on demand. But a fixed displacement compressor (or a variable one on max demand), when it's on, will take the power quoted. The only exception that I know of was some Honda engines that ran to 8000rpm where I think it shut down the compressor at 7000rpm as with the over gearing of the compressor it would be above it's 8000rpm maximum rating.
Go and quickly rev your engine to above 4000rpm, and you will see the compressor disengage, hold it there and it will re-engage. Rev it up slowly and it won't.
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Can you really hope for 5C from the vents? Surely the external ambient has got an effect and all you can hope for is a certain temperature drop? I'm interested as I have a Passat with a presumably similar climate control system.A couple of years ago I measured around 12C
I did get 5 degrees JUST at the vents and the outside temp was 23 degrees.
I can appreciate that this may not be the case if the temp was 30c, but 12c is unacceptable under almost any circumstances in the UK climate and I would guess the system was down on efficiency for some reason.
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You won't get much better, for the simple reason that the evaporator must not be allowed to drop below zero degrees. So if they build in a tolerance of a couple of degrees, plus a temperature rise along the air path (it can get pretty hot behind the dash, and it's not insulated), maybe a bit of air from the heater matrix mixed in due to poor sealing on the blend flap, and you end up with 5deg.
The biggest factor affecting the cooling (assuming the system is working to spec) is the heat load from the sun. Just think how quickly the car heats up when left in the sun, even on a cool day. It's also not just the outlet temperature, but the total air flow. You could get -25* at the vent, but it's no use of the airflow is very low.
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