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After 2 very cold days followed by a relatively mild one today, I've been trying to work out the logic and threshold of stop-start being available.

On the 2 cold days (ambient temp -2C going to work), my oil was above 90C at about 7 miles into my 13 mile commute, and battery charge was a very healthy 14.2v, yet stop-start wasn't available until 11.5 miles in due to "high accessory consumption", or words to that effect (can't remember the exact terminology displayed).

I also noted today that at a tropical 6.5C ambient temp, stop-start was available at only 2 mins into the commute, despite the oil temp being "- - -" (below 50C) and battery voltage only being 11.6v. It seems to me then that a low ambient temp is far more important to the car than oil temp or battery voltage in determining whether to make stop-start available (surely battery voltage should be top determining factor?).


After noting all this, I was looking at the "consumer conveniences screen" for the first time and despite not having the aircon on, there's a scale of 0 to 1/4 gallon per hour, and a bar underneath about 40% of the scale labelled "aircon". So for my 35-40 minute morning commute, I would surmise that at that level, i'm using about a tenth of a gallon per hour with the aircon being on, or about 0.27 litres in 35 mins, when total use for my 35mpg 13 mile journey is 1.70 litres. That's a big proportion, surely that's wrong? If it's right and I can eliminate that aircon usage,, i'd only be using 1.43 litres, or achieving 41.6mpg.

I hadn't actually switched the aircon on, nor was the aircon light lit. As always, the venting dial was set to windscreen only. When I changed to any other venting setting, that consumer conveniences screen entry for aircon drops to almost nothing. If you set the temp dial to the bit where the red and blue zones meet (to denote ambient temp feed I would assume), the indicated aircon usage in the convenience consumers screen drops marginally when venting to the windscreen. When venting to windscreen and pressing the aircon button on, the convenience consumers indicated aircon usage didn't increase - that does imply that the aircon was already on.

When you pick up speed, the indicated aircon usage drops a little, as you'd expect - aircon is more efficient at speed.

I've never had issue with a misty screen, but then again if the aircon is always on because I always direct venting to windscreen (which seems to have the aircon on without indicating it is on, then I won't.

When I did switch the venting to any other setting, I did experience misting of the windscreen, with build up being slowest on windscreen + downward blowing.

If the ambient temps are reasonable over the weekend (to avoid misting), I will drive with the windscreen + downward blowing to see if I experience a discernable mpg difference.

So with all that in mind I do wonder whether those that seem to experience much better mpg than others on a like for like engine basis are using windscreen venting or another venting setting on the manual temp system, or are using climate control on a certain setting?

Maybe anyone not using windscreen venting settings also seem to have frequent windscreen misting issues?

Perhaps the RLHS (rain light humidity sensor) sends airconditioned air to the windscreen to keep it de-misted, while the climatronic is set to auto? Just thinking out loud here.

Do these cars not have an indicator to confirm or otherwise that the chiller is "enabled/available"? In my cars with auto AC I am "bad" at selecting max demist to windscreen then disabling the chiller so the AC light goes out - unless conditions demand that the chiller must be left on.

iichel wrote: Sat Jan 26, 2019 8:46 am Perhaps the RLHS (rain light humidity sensor) sends airconditioned air to the windscreen to keep it de-misted, while the climatronic is set to auto? Just thinking out loud here.

I don't have climatronic, I have the manual control. Convenience consumers shows heavy aircon usage with venting dial set to the screen only.

Indicated consumption (in convenience consumers) doesn't change whether the aircon button is set on or off while venting to the windscreen. The other 3 venting settkngs sjow negligible or no aircon consumption.

Likely climatronic will work similarly, especially in the Summer while trying to maintain a temp lower than ambient.

I'm going to see if avoiding having the venting set that way increases.my fuel economy appreciably.

I wonder if the aircon usage stops under heavy acceleration, when you can see the performance screen showing output maxing out at 147kW, or whether that figure is drive and aircon combined.

At wide open throttle detection the AC and alternator charge control are or can be inhibited - model trim level dependant, which as the GTI is the topic of discussion must be the case.

RUM4MO wrote: Sat Jan 26, 2019 10:36 am Do these cars not have an indicator to confirm or otherwise that the chiller is "enabled/available"? In my cars with auto AC I am "bad" at selecting max demist to windscreen then disabling the chiller so the AC light goes out - unless conditions demand that the chiller must be left on.

That's the odd thing - there's an aircon light, and that automatically goes on if you turn the temp dial to the minimum (and you can the press the AC button off).

You can turn aircon on or off as you please with the AC light which illuminates to say it's on, but with the aircon button illuminated or not, when venting is set to windscreen, the indicated aircon consumption in "Convenience consumers" remains the same (that value being about 0.1 gallons an hour).

monkeyhanger wrote: Sat Jan 26, 2019 10:49 am

RUM4MO wrote: Sat Jan 26, 2019 10:36 am Do these cars not have an indicator to confirm or otherwise that the chiller is "enabled/available"? In my cars with auto AC I am "bad" at selecting max demist to windscreen then disabling the chiller so the AC light goes out - unless conditions demand that the chiller must be left on.

That's the odd thing - there's an aircon light, and that automatically goes on if you turn the temp dial to the minimum (and you can the press the AC button off).

Does your aircon light automatically illuminate when you set the air direction to 12 O’Clock Windscreen only as it does on mine?

roywolfey wrote: Sat Jan 26, 2019 2:37 pm

monkeyhanger wrote: Sat Jan 26, 2019 10:49 am

RUM4MO wrote: Sat Jan 26, 2019 10:36 am Do these cars not have an indicator to confirm or otherwise that the chiller is "enabled/available"? In my cars with auto AC I am "bad" at selecting max demist to windscreen then disabling the chiller so the AC light goes out - unless conditions demand that the chiller must be left on.

That's the odd thing - there's an aircon light, and that automatically goes on if you turn the temp dial to the minimum (and you can the press the AC button off).

Does your aircon light automatically illuminate when you set the air direction to 12 O’Clock Windscreen only as it does on mine?

Only when I set temp dial to minimum while air direction is windscreen only. But as per my posts, light on or light off, the aircon is working overtime in the background.

monkeyhanger wrote: Sat Jan 26, 2019 3:38 pm

roywolfey wrote: Sat Jan 26, 2019 2:37 pm

monkeyhanger wrote: Sat Jan 26, 2019 10:49 am

That's the odd thing - there's an aircon light, and that automatically goes on if you turn the temp dial to the minimum (and you can the press the AC button off).

Does your aircon light automatically illuminate when you set the air direction to 12 O’Clock Windscreen only as it does on mine?

Only when I set temp dial to minimum while air direction is windscreen only. But as per my posts, light on or light off, the aircon is working overtime in the background.

That’s why I mentioned it, as in my car the A/C light light comes on when you set the air direction to 12 O’Clock ‘windscreen’ position irrespective of where the temperature dial is set. My reasoning is that your A/C is also coming on but the light is not necessarily illuminating in the same way that mine does?

as you know im he loan golf at the moment.

I checked it out last night and you are correct the air con, even if switched off, comes on when the selector is dialled to windscreen. even if you then switch the aircon off again, the consumer screen tells you that the fuel consumption stays the same, and the windscreen stays clear. so clearly the aircon is always on when you dial windscreen. its a good tip and would go some of the way to explaining why im getting very fluctuating fuel econ figures in the same car on the same drive just on a damp morning with the airflow directed to windscreen.

Thanks for that Monkeyhanger, good spot. that tip will save me fuel.

out of interest I noticed the golf 1.5 evo 150hp has the GTI sport screen with G & KW meter and lap timer. not sure why I don't think the 150hp car is a track car lol.

^ It should go someway to explaining my.persistently disappointing mpg compared to other people here, as my venting has been left in windscreen only by default.

Where at all possible (unless misting occurs), I'll be putting it to windscreen + downward cabin venting. Hopefully will see some mpg increases.

This kind of car ‘intelligence’ really irritates me. If I want the aircon on, I’ll turn the aircon on!

I’d always assumed that if you turn the air direction dial to windscreen and the air con comes on, that hitting the a/c button and turning the light off, the aircon would also turn off, but as you guys have experienced the convenience consumers still shows energy draw from the A/C despite the light turning off. It would seem that if the air direction dial is at 12 o’clock Windscreen position then the a/c is on irrespective of what you do with the controls.

To avoid the aircon light coming on at all, I never put the air direction fully to 12 O’clock instead leaving it a couple of clicks away. I can confirm there is no reading against A/C in convenience consumers in this posturing. So coincidentally I haven’t had the A/C on at all during the winter. This may go some way to explain why I have never seen the message to stay start stop is inactive due to convenience consumers, and maybe why other are reporting greater misting of windscreens and I also wonder if this goes some way to explaining some of the good mpg I have experienced compared to others, although I thing this last point is more to do with the nature and road conditions on my long daily commute.

Interesting. I hate demisting the windscreen as it turns off recycling hence fumes from the cars in front are taken into the cabin. I try and demist before driving off, then turn the blower to the three o’clock position, heating on, recycle on, window open. The air con dries the air too much. I do wonder how effective the air filter is, I don’t think it’s activated charcoal.

When I had the Citroen C3 on loan my lips got so dry they were bleeding and quite painful due I think to the air con.

roywolfey wrote: Sun Jan 27, 2019 4:13 pm This kind of car ‘intelligence’ really irritates me. If I want the aircon on, I’ll turn the aircon on!

I’d always assumed that if you turn the air direction dial to windscreen and the air con comes on, that hitting the a/c button and turning the light off, the aircon would also turn off, but as you guys have experienced the convenience consumers still shows energy draw from the A/C despite the light turning off. It would seem that if the air direction dial is at 12 o’clock Windscreen position then the a/c is on irrespective of what you do with the controls.

To avoid the aircon light coming on at all, I never put the air direction fully to 12 O’clock instead leaving it a couple of clicks away. I can confirm there is no reading against A/C in convenience consumers in this posturing. So coincidentally I haven’t had the A/C on at all during the winter. This may go some way to explain why I have never seen the message to stay start stop is inactive due to convenience consumers, and maybe why other are reporting greater misting of windscreens and I also wonder if this goes some way to explaining some of the good mpg I have experienced compared to others, although I thing this last point is more to do with the nature and road conditions on my long daily commute.

I'm not sure what venting mode the car would put itself in if you are not on either of the defined modes at the 3, 6, 9 or 12 o'clock position on the dial. Putting it at 11 o'clock may result in no flaps or all flaps being open for venting, or a weighting between windscreen/downwards and wholly windscreen and not triggering aircon activation..

If you've never had yours in the 12 o'clock position for the aircon to be working pretty hard, then I'd say you were far more likely to experience misting, in cold or very wet conditions.

Twiddling with mine on Thursday and Friday morning after determining that aircon is always on in windscreen venting (12 o'clock on dial), I experienced misting in the other 3 modes - windscreen/down venting was the slowest to mist up.

Whereas having the a/c on is great for demisting, I find that there’s a tendency for the windows to mist up even more when the Engine is off and car stationery requiring even more demisting next time round. I try and manage without using A/C where I can and only use it when the none a/c venting is unable to clear the screen.