Morning folks

Bit of a strange one so seeking opinions if I may.

Tried the FBH in my 2016 L405 this morning via the remote fob. 1st press gave me fast flashing lights and second press got the usual slow flash and I heard things ‘fire up’

Left the car for just over 20 mins doing it’s thing but when I went out to get in and go for a drive the car was still very cold. It’s in a garage so no frost to clear etc etc but the interior was damn cold and the temp gauge on the dash was still firmly on the blue - cold air coming out of the interior vents.

Is this normal..? Does it need longer than 20 mins to warm up?

Any clues / advice most welcome.

Thanks Ash
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2016 SDV8 AB

The FBH will shut down if the battery is low. MY23 D350 HSE
On my 7th RR plus various other JLR vehicles

Thx Phil

And agreed - but it didn’t shut down. It was still merrily doing it’s thing and I could hear it standing beside the car. It’s almost like it was working but no wasn’t actually burning anything - no smell of burning diesel.

Thanks Ash
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2016 SDV8 AB

Two possibilities - you'd put it onto 'cool' so the sound was just the internal fan running, or the coolant control valve is stuck so there was nowhere for the heated coolant to go and the FBH was running but only heating the coolant in a very small circuit for a few seconds at a time until it reached the cutoff temperature - the FBH air fan and coolant pump would still run in this event.

Thx Phoenix

I used the remote fob so it’s only park heating I guess at this time of year.

Will have to check to see if there are any error codes but the fan was defo running

Thx Ash
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2016 SDV8 AB

It would depend upon how warm the ambient temperature sensor thinks it is. If the FBH failed to fire, (IIRC) it would retry twice then shutdown with a hard DTC and locked out, the combustion fan certainly wouldn't continue for over 15 mins after that.
It's unlikely that the coolant control valve would set a DTC unless it is open circuit as there is no position sensor to verify correct actuation.

Thx

Let me see if IID shows a fault code and I’ll go from there.

The ambient temp would have been around 1° as it was -1° outside

Will report back later Ash
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2016 SDV8 AB

Also check the actual values of the temperature sensors - might give a clue, or at least confirm they are reading accurately.

Right - not sure if this is going to be of any use but IID reported the following

Click image to enlarge

Well if the water pump isn't running, that would explain it - I'm fairly sure the FBH would/should fail to start if there is a detectable fault with it's circulation pump.
The temperature sensors I was referring ot are the vehicle ones, not the FBH ones but there's no point checking them if you have a DTC for the circulation pump- Interesting that both DTC's seem to have been triggered at the same time.