Hello everyone I wonder if somebody can assist me , I have a 2013 Jaguar XJL and the driver side seat heating is not working the cooling is working but not the heating , it would seem from some research on the forum etc it maybe a control unit a small black and grey unit with two screws , is this under the drivers or passenger seat and would this be the correct diagnosis , any help would be greatly appreciated, thanks all

Each seat has its own module, they are black and I believe will be labelled Volvo, they're driven by the climate control module which is grey and black. I believe the RHD vehicles the modules are under the passenger seat. If the passenger seat is heating then the fusing is OK if it isn't check R2 and F17 (20 amp) located in the boot. If a heater element in the seat fails then all those in that seat generally will. There are several diagnostic options but you need to find the correct connector and it is kind of hard to show an image of it without tearing mine apart. You are looking for connector C3HS02 (seat cushion under the seat someplace) and C3HS01 (backrest I don't know where this is beyond it is in or below the backrest). You can also use a diagnostic tool to get information from the modules about status of elements and sensors but I don't know which ones would do this as I use JLR SDD.

You need to check resistances and you need a decent meter for this not a £5 special.

This is for the drivers side ....
The cushion heating element is between pins C3HS02/1 and C3HS02/4, you should read between .99 and 1.32 ohms
The seat temperature sensor is between pins C3HS02/2 and C3HS02/3, you should read between 4000 and 10000 ohms
The backrest heating element is between pins C3HS01/1 and C3HS01/2, you should read between .67 and .90 ohms

Make sure you measure the cables disconnected not control module itself.

Thanks so much for this detailed reply and your help , so it would seem I have a climate control module here (see image) and not the module that controls each seats heating , I have a quality fluke multimeter so I will use your information and take a look

That is indeed the seat climate module - you should still have the other modules somewhere. The seat control modules are part number C2D2248, the climate module for the seats is C2D1586 - at least for my car they are.

Once again thanks , In your opinion is it at all likely that the climate unit maybe at fault causing my phenomena?

I would check the heated mats and sensor and if they check out fine the black module is likely to be at fault they are communication based, the C2D2248 handles the switching. You can get them off a certain auction site, even if it isn't that it doesn't hurt to have a spare. if one of the mats has failed the job is a bear as the seat must be dismantled.