Member Since: 15 Dec 2014
Location: Leicester
Posts: 135
Heater starts to blow cooler air
I thought this was just my imagination, but on a recent trip the Mrs commented on this too.
With the heating in manual mode (not auto or AC), if we set the temp to say 21 degrees, within a few mins of driving we start to get hot air. After some time, it begins to blow what feels to be cooler air out, noted by the fact that we have to increase the temp (say to 25) to start to get hot air again. So on and so forth.
I saw some threads on the D3 list for similar issues, but cant seem to find anything D4 specific.
No advice but my 2010 does this also. I recall reading that even with the ac off the ac pump isn't fully shut down. Still annoying that it starts to cool the cabin when you want it to stay warm.
29th Nov 2016 5:03 pm
Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
D4s can suffer from warm air behind the dash affecting the cabin temp sensor, so not that different to the original D3s. Sometimes the pipework behind the sensor becomes dislodged or crushed at manufacture or during a repair.
Land Rover - Turning Drivers into Mechanics Since 1948
Member Since: 28 Aug 2014
Location: Norfolk
Posts: 4400
What you're seeing, or rather feeling is the effect of the 'climate' control, which is actually just thermostatic control. You chose a temperature, and when the temperature of the air inside the car reaches, or actually exceeds the set temperature, the system blows cold to bring it down again. When the air temperature is too cold, it'll blow hot again to raise the temperature.
The system is not very good. The gap between the low temp (when it tries to raise the temp) and the high temp (when it tries to lower the temp) is called the hysteresis.
I've had cars with better systems (lower hysteresis), but I found the same as you. the changing temperature of the blown air is annoying to say the least.Richard
D3 SE 2007. Triumph 2.5Pi 1973. Ferguson TEA20 1948.
Discovery 2 4.0 ES 2001- Gone
Discovery 1 300Tdi ES '95 - Gone
Range Rover Classic '79 - Gone
29th Nov 2016 6:32 pm
Singh
Member Since: 15 Dec 2014
Location: Leicester
Posts: 135
Robbie wrote:
D4s can suffer from warm air behind the dash affecting the cabin temp sensor, so not that different to the original D3s. Sometimes the pipework behind the sensor becomes dislodged or crushed at manufacture or during a repair.
What do you do to diagnose this correctly, and or, how do you fix it?
29th Nov 2016 11:33 pm
Singh
Member Since: 15 Dec 2014
Location: Leicester
Posts: 135
rrhool wrote:
What you're seeing, or rather feeling is the effect of the 'climate' control, which is actually just thermostatic control. You chose a temperature, and when the temperature of the air inside the car reaches, or actually exceeds the set temperature, the system blows cold to bring it down again. When the air temperature is too cold, it'll blow hot again to raise the temperature.
The system is not very good. The gap between the low temp (when it tries to raise the temp) and the high temp (when it tries to lower the temp) is called the hysteresis.
I've had cars with better systems (lower hysteresis), but I found the same as you. the changing temperature of the blown air is annoying to say the least.
So it does this even if the heating is not set to AUTO? I would assume what you describe would be the true climate control function, but what I expect it to do in non-Auto mode is if I set the fan speed and temp to my desired value, it keeps pumping that out regardless until I change any of the settings?
Seems there is always monitoring of the air temp going on, regardless if using the climate control in auto or manual mode. I know in auto mode it also controls fan speed and air distribution, but it seems that from what you say, manual does not really mean manual.
29th Nov 2016 11:37 pm
lynalldiscovery
Member Since: 22 Dec 2009
Location: Maidstone
Posts: 7274
Ive had climate on a few different cars now and sometimes think the old three rotary knobs were just so much easier, you want heat turn the dial clockwise and it will keep blowing hot until you start sweating.
30th Nov 2016 8:07 am
FISHBOY
Member Since: 06 Sep 2010
Location: Kent
Posts: 754
Noticed exactly the same thing - car only seems warm when its set on high, but then gets too hot.
Set it to 25 - 28 and I feel cold air through so I put on high and switch it off when I start cooking.
Anyway of disconnecting something in the climate control/ moving the sensor?
30th Nov 2016 9:32 am
rrhool
Member Since: 28 Aug 2014
Location: Norfolk
Posts: 4400
Singh wrote:
So it does this even if the heating is not set to AUTO? I would assume what you describe would be the true climate control function, but what I expect it to do in non-Auto mode is if I set the fan speed and temp to my desired value, it keeps pumping that out regardless until I change any of the settings?
Seems there is always monitoring of the air temp going on, regardless if using the climate control in auto or manual mode. I know in auto mode it also controls fan speed and air distribution, but it seems that from what you say, manual does not really mean manual.
The temperature is always thermostatically 'Climate' controlled, even in manual. For it to be properly manual, there would have to be a physical control of a water valve, or an air mixing flap, and there simply isn't. It's all electronically/electrically controlled. I dont believe there is any cure, it was written into the control system at design.Richard
D3 SE 2007. Triumph 2.5Pi 1973. Ferguson TEA20 1948.
Discovery 2 4.0 ES 2001- Gone
Discovery 1 300Tdi ES '95 - Gone
Range Rover Classic '79 - Gone
30th Nov 2016 9:43 am
Singh
Member Since: 15 Dec 2014
Location: Leicester
Posts: 135
Thanks for that. Annoying to say the least.
30th Nov 2016 10:09 am
HammersnBlades
Member Since: 14 Apr 2013
Location: Almancil
Posts: 4
Blowing cooler air
This could be the start of the Water distribution Valve bonding breaking down. Its a plastic unit perched on top of the engine just above the fan.. If you notice fluid loss then its more than likely to be the issue..
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