Hope someone can shed some light on my latest issue as I'm at my wits end with this: - Vehicle is a SDV8 LWB MY 2016 and has 4 zone aircon and FFBH with remote heat/cool option. If I use the FFBH in a morning it warms the car as it always did, however once driving the heater is only getting lukewarm and even less so on the passenger side. Rear heating (high level and floor ducts) are totally cold. Switching aircon on/off makes no difference.


What I have checked/noticed so far: -

Had the aircon gas evacuated and showed 1150g removed and then regassed.

Engine water temp is normal (read on IID).

Flushed front matrix, no restriction noticed and no debris removed in flush process.

The 2 coolant lines to the front matrix seem to differ in temp (one is definitely hotter than the other). If the front fan speed is increased this is more noticeable.

Checked the diverter valve on the side of the FBH and confirmed as working although blowing down the ports suggests that there is more flow in one position than the other (took it apart and the plunger moves fully in both directions (5mm or so).

With the rear aircon switched off noted that the rear auxillary heater matrix has one pipe hot and one slightly less hot. As soon as the rear fan is switched on the temp of the one pipe goes cold (like the heat has been drawn from the matrix by the fan, and similar scenario to the front). If I switch the rear climate off, the front heating improves slightly.

It's almost like there is no coolant flow around the system although I have noted that the FFBH coolant pump is running but fully appreciate that this isn't designed to circulate cooland around the whole system.

If anyone has suffered anything similar then please shout up as my LR Indie is muttering about removing the dash and changing the matrix, which I don't really want to have done for all the obvious reasons (and I don't think it will cure it)!

Many thanks for taking the time to read my ramblings! L405 SV Autobiography LWB SDV8, finished in Aston Martin China Grey by ETO division.

Might be worth a look - &t=275s Got - 2017 SDV8 Autobiography in Loire Blue
Had- 2008 TDV8 Vogue SE in Java black
Had - 2007 S/C in Stornoway Grey

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Last edited by Phoenix on 23rd Dec 2023 10:26pm. Edited 1 time in total

Thanks alanm_3 & Phoenix for the replies, very interesting video, pretty much what I did, took the valve off and tested it and assumed it was ok as the solenoid operated. As Phoenix says, maybe mine is restricting some of the flow, hence I've ordered a genuine valve and will get it swapped out this week.

I initially thought it was the compressor pressure relief valve sticking as I have read about this causing similar problems. I saw there was a bulletin on topix for this, so did update the HVAC ecu via SDD as this apparently cures the compressor problem, in my case no difference.

Will keep you guys updated on how it goes! L405 SV Autobiography LWB SDV8, finished in Aston Martin China Grey by ETO division.

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Last edited by Phoenix on 23rd Dec 2023 10:27pm. Edited 1 time in total

I've got a mate who's the parts manager at local MD, so I'm not much more than that, just hope it cures it!!

Thanks again, Phoenix, you seem to be the "go to man" for anything 405!! L405 SV Autobiography LWB SDV8, finished in Aston Martin China Grey by ETO division.

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Last edited by Phoenix on 23rd Dec 2023 10:27pm. Edited 1 time in total

Well, replacement diverter valve turned up today, popped it on and heating back to normal
Not sure what was wrong with the old one to restrict the flow that much as to cause a near complete loss of cabin heat, the solenoid operated along it's full travel, so can only maybe think the rubber seals were swollen??

judging by the 3 superceded part numbers from original, it's design has 'matured' over the years

Anyway, many thanks to all for helping me out, it's so nice to be back in the warm! L405 SV Autobiography LWB SDV8, finished in Aston Martin China Grey by ETO division.

Last edited by 4RRS on 1st Dec 2023 10:28pm. Edited 1 time in total

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Last edited by Phoenix on 23rd Dec 2023 10:27pm. Edited 1 time in total

I seem to be having the same issue! I have a 2016 LWB 5.0SC that I purchased 2 days ago. My wife was taking it to work in the morning and said theres no heat from any of the vents (front or rear). Im not 100% on which heater hoses are which but one of them was very cold to the touch, the one coming over the valve cover was hot as hell, and the hoses coming off the preheater assembly were definitely warm to the touch but not quote as hot as the one coming over the valve cover.

You said the diverter valve solved your problem but the link posted by Phoenix is for a pump? The video definitely shows a diverter valve though so which exactly did you replace and would you be able to provide me with a part number so I can order the part as well? Thank you

Sounds like the same symptoms. I noticed Phoenix posted a pump and looks nothing like the diverter valve, which is what I replaced.

Part number callout 18495, LR part LR167749 in the below diagram. This is upto chasis HA999999 so should suit yours.

https://store.landrover.com/parts/index/pa...and-rover/

I paid just over £100 form my local dealer.

Hope this helps. L405 SV Autobiography LWB SDV8, finished in Aston Martin China Grey by ETO division.

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Last edited by Phoenix on 23rd Dec 2023 10:27pm. Edited 2 times in total

Thank you so much for your guidance! I greatly appreciate it!