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Discussion Starter · #1 ·
After a few issues with my drivers seat I thought I'd do a bit of a how-to on how to diagnose and enact a repair.

Problem/Fault

Firstly, this issue normally manifests itself as a failure of one of the seat heaters, the cooled mode generally works.

When turning on the heated seat, it will generally run the fan for a second or two, and then shut down. Please note that it will prevent both seats from operating, even if one of them is actually ok. Once the ignition has been cycled it will then be available to try again, but will do the same again.

Description of system.

The system is controlled by a module underneath the drivers seat (RH seat).

In each seat there are two units, one for the seat base, and one for the seat back. These both incorporate a multi-speed fan (with filter) and a Peltier heating/cooling unit and plastic duct.

The fan blows air across the Peltier which has two sides, both with their own exhaust. One side is blown into the seat and the other is an exhaust for the Peltier.

Depending on the direction of the current, one side cools and the other side heats. This gives active heating and cooling. I believe the later systems had heat pads with a circulating fan. Cooling was passive/ventilated.

The under seat/cushion units are handed, but the seat back units are identical.

Diagnosing

It seems that the vast majority of failures seem to be on the seat back unit. The Jaguar seats don't seem to suffer too much, but there are failures (including my own).

Range Rover and probably other JLR products use the exact same setup and it seems more common on Range Rovers.

Luckily with the seat back units being identical, it should be a case of swapping out the offending side with the known working side. Obviously the drivers side will by far get the most use.

If you've already got the units out and want to test them with a multi-meter then have a gander at this thread for more in depth info.


Basically though, the two middle wires are for the thermistor and the blue and yellow on the outer side are for the peltier itself. If you've a very high resistance across the peltier then it's likely failed. Low to virtually no resistance and it's probably ok.

I've not heard of any thermistor failures, but mine generally read between 1-1.4K Ohm at room temperature. Dropping down when heated with a hairdryer.

Removals

Firstly, if you've not done this before, it's not difficult to gain access to the seat back unit, but can be a bit fiddly.

The only two tools you'll need is a T20 torx driver. I used one on a ratchet as it saves you taking off the whole seat back, and a flat headed screwdriver.

The flat headed screwdriver is to make separating the connector easier but not really required if you've got some decent nails.

Move the seat forward and tip forward and release any lumbar support.

Sitting in the back of the car, firmly push the plastic seat back cover down. This should allow you to gain access to the inside of the seat back.

If you want to go further, then you can take off the outer side panel and remove the whole seat back, but it's not really needed.

The peltier is in the middle of the seat towards the right hand side and is held in by 3 torx screws. The top two are easy to locate/see but the bottom one is a bit hidden.

Given that I left the seat back, it was much easier to use a T20 torx bit on a 1/4" ratchet.

Lift the whole unit up (you may need to push it forwards into the seat to get the screw supports past).

I found the best way to do it was to lift the whole unit right up first and then pull the fan unit out and down. The middle bar is what makes this difficult.

Repairs.

The first step is simply to swap it with the opposing side and check its function, as I said its very likely to be the drivers side seat back that's failed as that's the most used.

Put the passenger side into the drivers seat and test. If it's confirmed that it's the drivers side unit that failed then you'll need a replacement peltier unit.

I've managed to source a new peltier unit from here.

 

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Discussion Starter · #2 ·
You'll need a T6 torx bit to open up the peltier unit.

Here's a few photos of my repair....

184615

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So after fluxing, tinning and soldering the wires together, along with some heat shrink. I tidied up the wires with some small cable ties.

Tested it and we're all up and running again fully.

Hopefully it'll help some others in the future, and I'll try and answer anyones questions as best I can :)
 

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2021 F-Pace P250 SE R-Dynamic, 2004 XK8 Coupe 4.2
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That looks really comprehensive, well done.
 

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Ok thanks. Do I definitely need a soldering iron?
You could possibly use butt crimps. But solder and heat shrink will be neater and more permanent. Buy an iron and practice on some scrap wire. Plenty of vids out there I'd expect to give you some tuition.
 
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2021 F-Pace P250 SE R-Dynamic, 2004 XK8 Coupe 4.2
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Soldering is something I’ve been practicing whilst in lockdown. Getting better but as my school report - could do better.
 
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Hope u are still active on here, great artiicle. I just picked up a rr vogue 2012 supercharged and all the controls appear to be dead. No lights anywhere. Fuse is OK. Is the a relay hiding for this system or do u have any other suggestions?
 

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Discussion Starter · #10 ·
I'm still here....

This is a guide for a 2008 XF, so I've no idea what the exact setup on your car will be.

There is a module under the seat that controls this on the XF though that has the relays in. There could be something similar on the RR but can't help much more than that sorry.
 

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Slide seat forward, remove reaf bolts, slide seat back, undo front bolts. Tip the whole seat back to rest on rear seat, no need to disconnect anything. You can then get to some screw to drop down the panel under the seat.
If your repairing the peltier unit or fans you only need to remove the seat back, no need to remove seat to tip backwards!
 

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Discussion Starter · #13 ·
You need to unbolt the seat, you don't need to totally remove it from the car as they're damned heavy, but they'll tip back and spin around out the way. Just be careful you don't catch the rails on anything.
 
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