Some seem to sell the car and move on, others try to fix it but don’t, others think they have fixed it.
There are various potential diagnoses but not one consistent one. Have I missed anything?
So far I’ve found people saying it was the following:
Heater matrix needed flushing out (dash out job)
Interior temp sensor by steering wheel needs a foam shroud to prevent it warming up (dash out job)
Misting sensor on windscreen not working
Incorrect outdoor temp readings throwing things out of whack (no idea if there’s a fix)
I have a single fault on my IId- misting sensor on windscreen not working. I struggle to believe this is the cause.
Any newer ideas? I know back in the day these cars were new Dealers had them in but few seemed to fix it.
Thanks1998 Defender 110 TUM HS FFR Hard Top XD WOLF
2016 Discovery 4 HSE
1982 Series 3 2.25 Petrol Hard top- Oscar, as featured in Classic Land Rover Magazine for 7 months
If (big if) I've understood it correctly, the in-cabin sensor is NOT the slotted thing near the steering wheel - that is simply a vent for a tube that leads to the sensor.
I've wondered if vacuuming this tube (or blowing air through it ?) would shift any dust/fluff that has collected in the tube and prevents the sensor actually measuring the in-cabin temp ?
25th Feb 2024 6:45 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5042
There may be something in here which might shed some light (or better still, heat) on the problem.
Thanks. I’d read that all before. As I say, no one seems to fix the issue1998 Defender 110 TUM HS FFR Hard Top XD WOLF
2016 Discovery 4 HSE
1982 Series 3 2.25 Petrol Hard top- Oscar, as featured in Classic Land Rover Magazine for 7 months
26th Feb 2024 8:18 am
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 5042
Unplug the mist sensor and see if that changes anything other than a related code.yµ (idµ - eAµ) ψ=mψ
26th Feb 2024 8:35 am
DaveJLBI
Member Since: 07 Mar 2014
Location: Clare
Posts: 682
Haven't had it done in a D4 but in the D3, the dash does NOT need to come out to flush the matrix. I had it done on my D3 several years ago and it made a huge difference. But don't ask me the details, it was done for me in my local indie (Limerick / Ireland)
26th Feb 2024 10:30 am
Gary_P
Member Since: 03 May 2016
Location: Kent
Posts: 1660
The outside temp reading 3 degrees higher than actual is a separate and more serious fault. It affects when certain other functions of the car kick in automatically, like windscreen and mirror heaters for instance. I’ve seen people have had this fixed.
On cabin temp, I’ve also read a lot about it as mine is borderline working properly. I have it on manual and turn the temp right up as far as I need it. I ignore the temp numbers (treating them as comfort numbers) in the centre of the dials and just wind it up as far as necessary. I’m often at 26 this time of year.
Keep us updated on anything you find.Gary
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Discovery 4 HSE 2016MY
26th Feb 2024 10:45 am
RRUK Site Supporter
Member Since: 16 Aug 2005
Location: UK
Posts: 676
I often have mine at 28 both sides yet the windscreen and top side vents seem to blow cool air.
I quite often find the tops of my legs are cold, like cold air is falling down on them.1998 Defender 110 TUM HS FFR Hard Top XD WOLF
2016 Discovery 4 HSE
1982 Series 3 2.25 Petrol Hard top- Oscar, as featured in Classic Land Rover Magazine for 7 months
26th Feb 2024 11:05 am
Gary_P
Member Since: 03 May 2016
Location: Kent
Posts: 1660
Yeah, welcome to the world of D4 driving in Winter. Is that on auto or manual?
I find Auto just doesn't work for me as it move airflow around the system.
On longer journeys there is a regular fiddle with temp and direction settings. Luckily the co- pilot takes care of that.Gary
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Discovery 4 HSE 2016MY
26th Feb 2024 11:13 am
RRUK Site Supporter
Member Since: 16 Aug 2005
Location: UK
Posts: 676
I use Auto most of the time, sometimes go to manual if its just not getting warm enough.1998 Defender 110 TUM HS FFR Hard Top XD WOLF
2016 Discovery 4 HSE
1982 Series 3 2.25 Petrol Hard top- Oscar, as featured in Classic Land Rover Magazine for 7 months
26th Feb 2024 11:26 am
KPTV8
Member Since: 05 Feb 2012
Location: Itinerant !! (Scotland/Donegal)
Posts: 187
Yes, such a shame to find the breed doing BACKWARDS evolution !!
I had three D3s with wonderful heating/cooling, but my MY 2010 D4 is often far from cosy.
At present I just set to AUTO and wind-up the temperature setting to 25C on cold days; havn't yet pinpointed where lurks the flaw.
I notice the warm air flow is much slower to BUILD after engine start, compared to my D3s - so I'm wondering if the thermostat (presumed !!) which diverts coolant through the matrix is either opening late, or is otherwise constricting coolant flow through the heating system.
Ages ago I had a FABULOUS P6 V8 manual with near-identical symptoms. Christmas Eve, Staples Corner to Princes St. (Edinburgh) in 5 hours was fab - but FROZEN KNEES !!!!!
26th Feb 2024 12:29 pm
Gary_P
Member Since: 03 May 2016
Location: Kent
Posts: 1660
Mine will suddenly go colder when we start a faster bit of route ) motorway). Almost like the airflow direct from outside is not shut off.
To summarise , with ref to the OP's question, it seems we haven't solved it, but we have work arounds.Gary
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Discovery 4 HSE 2016MY
26th Feb 2024 2:07 pm
RRUK Site Supporter
Member Since: 16 Aug 2005
Location: UK
Posts: 676
I've disconnected the fault-code inducing Humidity sensor and will monitor performance but I doubt it will make any difference.
I have been told by a reputable indy garage that the majority of times on the D4 its a partially blocked heater matrix, which is a dash out job1998 Defender 110 TUM HS FFR Hard Top XD WOLF
2016 Discovery 4 HSE
1982 Series 3 2.25 Petrol Hard top- Oscar, as featured in Classic Land Rover Magazine for 7 months
I am sure I have read somewhere that this doesn't have to be a dash out job.
Good luck
NJSS
26th Feb 2024 5:17 pm
Gary_P
Member Since: 03 May 2016
Location: Kent
Posts: 1660
Excellent. Perhaps we can have another go at this ! Keep us informed. It’s never been unbearable in my car, just a minor nuisance.
I believe a lot on here have had problems from new (like mine) , which would mean they must be coming out of manufacturing with a blocked matrix. My money is on a design change/ fault in manufacturing.
Mine never had the outside temperature issue by the way . Some poor people had both issues.Gary
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