During my first reasonable length drive post lockdown, I noticed the cabin temperature was higher than I wished, and on performing the diagnostic on the HVAC unit, it is showing error 12 "Ambient temperature sensor".
I was initially confused, as the outside temperature gauge appears to show a plausible value, but some searching on google suggests that there are in fact two temperature sensors. Does anyone know whether this is correct?
Also, does anyone know whether HVAC errors automatically clear when the fault goes away, or is there a clearance procedure?
Finally, does anyone have experience of this fault, and whether the sensor does fail?
Many thanks in anticipation.

 

That might mean the little sensor by the steering wheel? This has a little fan and can get very clogged up with fluff and dust that can be cleaned by a bit of compressed air.

 

There are 2 temperature sensors in the system

One in the left front wheel brake cooling duct . this measures the outside air ( ambient )

One in the panel below the steering column with about a 1 inch square grill you can see , this measures the cabin temp or the target

It's my opinion that because of the environment the brake cooling duct sensor connector is exposed to the sensor value can be so far off expected values it would give you a flag or code

Not so much for a clogged cabin temp sensor which would be slow to respond

Someone had a good pic of the cabin sensor and how clogged it can be like mine was

see page 98 and 100 and 110

They have the X308 V8 system mixed in the guide but they work the same

http://www.jagrepair.com/images/Trai...des/703_SG.pdf




Editing

 

Thanks Guys.
I am up to speed with the cabin temp sensor or aspirator as it is called, and will be giving it a clean for good measure.
The screen on the HVAC module which shows the selected cabin temperature, as you know, also shows the external temperature when the button is pushed. Mine is showing an external temperature which seems correct. Somewhere I have read that this value comes from a sensor in the right brake duct, and that there is another sensor in the left hand duct for "ambient" temperature which the HVAC uses to help regulate the cabin temp. Does anyone know if this could be correct? The Jaguar classic parts catalogue is not at its most helpful, but I can find two sensors listed, one with a cylindrical shape, LNA7605AB, and one a bit like a mushroom, LNA5700AC.
It would seem odd to have 2 sensors for external temperature, but stranger things....

 

I recently cleaned the interior temperature sensor and found it completely filled with dust, fluff and grass.
It's a relatively easy cleanup job. you need to remove the lower panel below the steering wheel to get to it. It took around 25 minutes to complete, using a 1 inch paint brush to clean it up.
I didn't see a huge difference once it was all back together, but the temperature readings are more realistic than before.

Here are the before and after pics I took

 

Ref page 138 of the 96 wiring guide the ambient temp sensor wiring goes through connector BL1 and LS1 which are both on the left side , no difference between LHD and RHD

Turns out to be 4 temp sensors , 2 being inside the evaporation plenum if you look across the top of the schematic

Ref wiring breakout sheet

pin CC30 - 11 ( in - car temp sensor ) and pin CC30 - 12 ( evap ) respond the same and are thermistors

Pin CC30 - 6 ( heater matrix )

Editing

 

I don’t know if it’s different or helpful but this the document for the 300 system
http://www.jagrepair.com/images/Trai...VeJJdZ7YSVs2N8

 

Thanks Cafcpete, that manual is gold dust!
The code 12 was stored, and once I cleared it, it has not returned, which leaves me with just code 23, which is low refrigerant, which I know about.

Thanks all