I thought I’d share my experience with the P400e HV heater. I bought a Sport about 18 months ago and ended up rejecting it as the HV heater had failed and they were on 6 months back order. It’s a £1500 repair at JLR and £600 of that is labour as they quote a few hours (it took me 20 mins last time!).

I’ve recently bought my L405 P400e and got it in summer when the issue isn’t as noticeable.

Symptoms - the car SHOULD run and drive from first start on EV mode, provided there’s enough charge and the aux battery is good. If the aux battery isn’t good it can run on engine to charge it now and again. For £60 I just replaced mine.

When the HV heater has failed it will use the engine to warm the car to whatever temp you ask for via the controls. If you turn off the heating completely and it runs in EV mode normally, then this heater has failed.

I tried a couple of second hand ones and it highlighted how frequently they fail as both were the same as mine (one was manufactured in 2022!). The offending part:

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That's a very good write up
Is there a section where things like this can be stored for future reference, rather than trying multiple keywords to search or is it just me who struggles to find things

Heroic - great write up and just what I need to do.

Out of interest what is the procedure to bleed the air from the coolant system?

Many thanks

There are three bleed screws (two to the left side of the engine and one above the FBH back left. Just open them when running to let the air out.

Incidentally, when the bonnet is up it disables EV mode so you can run the engine. My Previous RR's!
2018 P400e Autobiography
2008 TDV8 Vogue
2006 TD6 Vogue
2007 TDV8 Vogue
2007 RRS (I know, it doesn't count!)
2005 4.4 Vogue on LPG
2005 TD6 Vogue
2003 4.4 Vogue
2001 4.6 HSE
2000 2.5 DHSE
1999 4.6 HSE
1997 4.6 HSE on LPG
1995 2.5 DSE
1989 3.9 EFI classic
1988 3.5 EFI classic

Thank you for this report as I've just stumbled upon exactly the same issue. My P400e does not start in EV/Hybrid mode and with the temperature went down it runs 90% on ICE. It starts in EV (Hybrid, with no EV button active) with climate off, so apparently my HVH is down, waiting for the code reader delivery to confirm.

Can you please make a picture of your new unit, what model it is? I'm struggling to find info on how to pick a proper model, I know its been updated to "Gen. 1.5".
My original is HVH 50 Plus
Discovered online:
HVH 50
HVH 70
HVH 50 Gen 1.5
HVH 70 Gen 1.5
Not clear what that "Plus" in my stock part means, can't find the "Plus" version on sale. Search by partnumber provides the list of vendors selling the part, but no one states if it is 50 or 70, Gen. 1.5 or no.
So, can you please make a pic of your new part & possibly give a hint where you got it?

Mine:

Hi, the part number for the newer version of your heater is in the original post. If you google that number you’ll find a few on line. It’s a main dealer part, but I bought mine from a LR parts specialist called landranger. New genuine LR part has 2 year warranty. I think my original item was 50 plus, but the new part is 70. I can’t picture as it’s installed. My Previous RR's!
2018 P400e Autobiography
2008 TDV8 Vogue
2006 TD6 Vogue
2007 TDV8 Vogue
2007 RRS (I know, it doesn't count!)
2005 4.4 Vogue on LPG
2005 TD6 Vogue
2003 4.4 Vogue
2001 4.6 HSE
2000 2.5 DHSE
1999 4.6 HSE
1997 4.6 HSE on LPG
1995 2.5 DSE
1989 3.9 EFI classic
1988 3.5 EFI classic