bpman wrote:

thanks Eric your filing system is quicker than mine

Actually, it was you Steve who sent it to me And I filed it in my dedicated Defender folder......

Eric You never actually own a Defender. You merely look after it for the next generation.
http://youtu.be/yVRlSsJwD0o
https://youtu.be/vmPr3oTHndg
https://www.youtube.com/watch?v=_GtzTT9Pdl0
https://www.youtube.com/watch?v=ABqKPz28e6A
https://www.youtube.com/watch?v=rLZ49Jce_n0
https://www.youtube.com/watch?v=XvAsz_ilQYU
https://www.youtube.com/watch?v=K8tMHiX9lSw
https://m.youtube.com/watch?v=dxwjPuHIV7I
https://vimeo.com/201482507
https://www.youtube.com/watch?v=ZSixqL0iyHw

Liberace wrote:

Just joking on the subject, but I have a question. My 2012 110 blows cold air on the passenger side dash and floor vent after a few miles on the highway at speed (100 km/hr). Been this way all winter (which is my first).
Some of you might recognize I'm the one that had the engine failure/replacement last month and with the new motor in is no different. I tried all different settings including recirc to no avail. The drivers side is always warm. Once off the highway at slower speeds passenger side returns heat again and works as it should. Airflow is normal between the two sides so I dont think there is a disconnected hose.
So the passenger (usually my wife) gets quite annoyed on trips.
Is this normal on the post 2007 defenders, and is there a way to fix?
Thanks much,
James

Just PM'd you the fix

Edit: I am surprised that this problem actually persists. Had understood that LR had changed the production and either put a different heater matrix, or added this simple fix at the production process by 2011 models already....
Apparently wishful thinking from those engineers  You never actually own a Defender. You merely look after it for the next generation.
http://youtu.be/yVRlSsJwD0o
https://youtu.be/vmPr3oTHndg
https://www.youtube.com/watch?v=_GtzTT9Pdl0
https://www.youtube.com/watch?v=ABqKPz28e6A
https://www.youtube.com/watch?v=rLZ49Jce_n0
https://www.youtube.com/watch?v=XvAsz_ilQYU
https://www.youtube.com/watch?v=K8tMHiX9lSw
https://m.youtube.com/watch?v=dxwjPuHIV7I
https://vimeo.com/201482507
https://www.youtube.com/watch?v=ZSixqL0iyHw

blackwolf wrote:

There are really two fundamental design problems with the Puma heater which give rise to its two characteristic "issues".

Firstly, the inlet and outlet pipes to the heater matrix are both on the left hand side of the vehicle (the heater is identical on both LHD and RHD vehicles). Due to the size and design of the heater box and the placement of the matrix, all the air which comes out of the RH footwell vent passes through the RH side of the matrix, and all the air coming out of the LH pipe passes through the LH side of the matrix. The fact that the inlet and outet coolant pipes are on the left, and the flow characteristics of the matrix, mean that the LH side of the matrix runns hotter than the RH - by the the coolant flow, if any, reaches the RH side of the matrix, it has already lost most of its heat to the LH outlet pipe airflow. The inevitable result of this is that irrespecitve of whether the vehicle is LHD or RHD, the air coming out of the left footwell vent will always be hotter than the air coming out of the right footwell vent, unless the temperature is set to full flow and then engine is producing massive amounts of heat (see below).

The LR service bulletin mentioned above is intended to "solve" this issue, but all it actually does is block the air passages through the LH side of the heater matrix (where the hottest air originates) which will slightly reduce the heat emerging from the LH footwell vent. It does nothing at all to address the fundamental design problem and really is a classic bodge. Also, despite the fact that there is no difference in heater design between LHD and RHD cars, LR specifically state that the modification is for LHD vehicles only! Presumably only driver comfort is important, the passenger can go hang!

The second problem arises with the inherent efficiency of modern diesel engines, and the (incredibly complex) flow characteristics of the coolant in the TDCi engine. This results in a much wider range of coolant temperatures under "normal" driving conditions - the engine produces relatively little waste heat under light loads, but a fair amount when working hard. So, after going downhill the coolant will be at a significantly lower temperature than after climbing a hill (the temperature gauge on the dash is electronically controlled and programmed to remain on "normal" over a wide range of temperatures). The result of this is that the temperature of the coolant entering the heater will vary considerably according to what the engine is doing, and this causes the output temperature to fluctuate widely, especially if the flow through the heater has been reduced (by setting the flow control valve - the hot/cold knob) to a mid-range position.

The combined result of these two "features" is a heater which will never really be controllable and is not really satisfactory, and which blows air which especially in midrange setting fluctuates widely in temperature, and which produces air from the LH side vent which is generally significantly hotter than the air from the RH vent.

I believe that most modern cars (at least the relatively high-end ones with some form of climate control) use a system where there is constant full coolant flow through the heater matrix, and the desired output temperature is achieved by blending cold air (which hasn't passed through the matrix) with full heat hot air (which has) by means of a thermostatically controlled flap arrangement. This will produce a more-or-less constant output temperature irrespective of engine temp and working conditions. In the case of the Defender, the "temperature" control is nothing of the sort, it is just a flow regulator of the coolant through the matrix, and there is no form of proper temerature regulation at all.

As far as I know there have been no fundamental changes made to the heater since the Puma was introduced, and although is it possible that the latest ones already have the LH side of the matrix blocked off, I don't think that the MY13 heater will perfom any better than the MY07.

Also, I don't hink that having aircon makes any difference to the heating issues, since the heater is fundamentally the same.

There really doesn't seem to be and practical solution to this either. I have looked at thermostatically-controlled flow valves to replace the existing one, but there doesn't seem to be any readily available practical option. I have looked at fitting some kind of tubulence device of mixer in the hot side of the heater box, but there isn't room. I am sure that it would be possible to design a better heater that woudl fit, from scratch, but ultimately it doesn't really seem worth the effort. The existing one does, after all, produce more heat than earlier Defenders, and is, defective as it may be, it is still the best heater yet fitted to a Defender-type Landrover!

Top write up!  Darren