It seems from reading various posts on this forum and our sister site Disco3 that a faulty brake light switch can be responsible for a wide range of odd symptoms ranging from engine fault messages, suspension faults including lowering and going into limp mode, HDC fault messages and in my case just a heart-stopping momentary complete loss of power at motorway speeds sometimes - but not always -accompanied by the ubiquitous 'HDC fault - system not available' message and if cruise was engaged it would cancel with the 'cruise control cancelled' message. The power loss really was just for a split second and the rev counter dropped a little and then picked back up. Because there was a bit of a thud - it can (and was) easily be mistaken for a gearbox problem but I now realise it is probably the fuel supply being cut - as the car thinks the brakes are being applied.

Changing the brake light switch is inexpensive and easy for all but the most phobic amongst us.

To change the brake light switch you will need:

New brake light switch (about £15) - part number XKB500110 (FoMoCo - interestingly enough)

Cross-head screwdriver

Small torch



First of all have a good look at your new switch so that you understand how it fits into the bracket; but don't mess with it:




Unlock the car and let it go to sleep

Wind the driver's seat all the way back to improve access

Locate the big rectangular trim panel with the 'crutch cooling vent' immediately under the steering column:



This panel is hinged at the bottom and held in place by two of those horrible Land Rover spring clips - one at each top corner.
Grab the trim panel by putting a couple of fingers in the gap by the steering column and using the other hand to pull quite hard first at one corner and then at the other until they release. Drop it down and remove it and then spend a few minutes finding the spring clips which will have pinged off and tried to hide from you.



You should now be able to see the brake light switch attached to it's bracket just above the brake pedal - this where the torch comes in handy:



Note that the switch sits at an odd angle but that is how it goes!

At this point you might find it useful to loosen the lower trim panel by releasing the two turn buttons just by using the screwdriver to turn them back about half a turn. The panel won't come off but you can pull it down a bit in the middle.

Now reach in (small hands are a bonus here) get hold of the switch and turn it CLOCKWISE a quarter turn until it releases from the bracket and carefully release the wiring plug from the switch - little bit of gentle levering with a flat blade screwdriver helps to get it started but don't use any force.

You should now be able to see the aperture in the bracket that the switch locates into:



Next - taking care not to press down on the brake pedal - carefully insert the new switch into the aperture and when you are sure it is fully home against the bracket turn it ANTICLOCKWISE until it stops (approx. a quarter turn)and looks like the picture above showing the switch in it's original position. The plunger will have popped out and engaged with the brake pedal

Line up the wiring connector and push it back into the switch until it locks.

Gently tighten up the two turnbuttons on the lower panel.

Replace the spring clips on the upper trim panel if they pinged off:





Clip the trim panel back on.

Take the car for a spin to see if the problem is fixed. If it is - adopt a suitably smug expression whilst punching the air and repeating YES!! and go find yourself a cold beer.

I had to take the old switch apart to see what the problem is. Inside there are actually two switches. There is a switch comprised of two sliding contacts which looked as good as new and look designed for low current (so probably connected to the ECU?). The second switch has more substantial contacts designed for a higher current so probably turns the brake lamps on (look a bit like old style distributor contact points) and showed signs of arcing and were blackened. Here's they are still in-situ:



and here they are separated from the switch body:



The signs of arcing are clearly visible on the adjacent part of the switch body:



If you were to have this problem and unable to get hold of a new switch it might even be possible to just clean up the contacts as a temporary fix but you would have to be very careful not to break the switch when dismantling it. 2008 MY Java Black TDV8 HSE

Thanks for this "how to" guide Paddi

Driving home from Cornwall I had the dash light up like a Christmas tree several times. HDC unavailable, transmission fault and suspension lowered also cruise not re engaging.

Each time it happened I had just braked for one of the many roundabouts on the A303. It seemed to occur under really light or gradual braking

Got home and hit the search on here and read this guide, visited my local dealer today £21 inc vat for the switch and 5 minutes following your guide all sorted

Opened the old switch and the same arcing was visible inside that you have in your picture

Just wished I had picked up some spare trim clips as two of the disappeared never to be seen again, anyone got the part number

Cheers Rob TDV8 now with extra grin factor thanks to Alive Tunning: Gone but not forgotten

Result! Well done. Many sellers of the trim clips online but they can be obtained from site sponsor Duckworths at the best price. 2008 MY Java Black TDV8 HSE

Paddi

Cheers for this. Just changed my switch which took about 5 mins. Would have taken a lot longer without the help.

Paul 2006 Supercharged

Paddi, Thanks you for your advice, worked a treat. Tried it yesterday(Christmas Day), and it solved the brake light problem cleared the fault lights and allowed the suspension system to work. I took the switch apart very carefully and the contacts on the right hand side of the switch were badly burnt, cleaned them with small screwdriver and re-fitted. Will order new switch when parts dept opens as this is obviously a common problem. Strange that it should throw out so many other systems !!

Cheers for this post I've just followed it and replaced my dodgy brake switch by following this, I thought it was guna be a big job but turned out a doddle  Java black 2006

This is a great thead!

Having the same problem at the moment so will be ordering the brake light switch and fingers crossed all will be well AGAIN in Range Rover Land til the next fault  RRS SUPERCHARGED, 22 INCH ALLOYS, JAVA BLACK, FULLY COLOUR CODED
EVERY POSSIBLE SOFTWARE UPDATE INCLUDING - BLUTOOTH UPDATE, SATNAV ON THE MOVE, CLOCK ON DASH, 3 CLICK FLASH, GEARBOX RESET, COMPRESSOR UPDATE AND SUSPENSION LOWERED,
BLACK CODE RE-MAPPED, AUTOBIOGRAPHY'D, NEW EXIDE BATTERY, NEW DENSO ALTERNATOR

iv changed the brake switch this morning and checked over the electrics again and the 'engine system fault' still appears on the dash board and it wont rev over 5000 revs:(

Just tried to replace brake switch and failed. My trim panel, 2006 SC, has two screws holding top of panel. The panel also goes behind side trims on both sides and it looks like the side trims have to come off. I can pull the panel down enough to see the switch but not so as to change it. Am I being a total idiot or have I a one off car. past personal chariots
TVR S1, TVR Chimaera, Mercedes 500SL, all sadly missed but age demanded easier access.

Hi, sorry to hear you are experiencing a bit of a problem.

Are you referring to the trim panel with the 'crutch vent' as in the second picture of the guide? If so - yours must be very different.

Can you post a picture?

Anyone with an SC who can comment on trim panel in SCs? 2008 MY Java Black TDV8 HSE

A fantastic "How Too" post Paddi

For the sake of less than £20 I will be changing out the switch on my Discovery 3 as a preventive maintenance item.

Jim

Sorry all. I am a complete idiot. I was trying to take off the wrong panel. I can add a bit of useful, I hope, information. Loosening the lower panel by undoing the two screws at the top and holding the panel open makes replacing the switch much easier. Thanks for reply.  past personal chariots
TVR S1, TVR Chimaera, Mercedes 500SL, all sadly missed but age demanded easier access.

Glad you sorted it out in the end

I figured that anyone with a history of TVRs must be fairly competent at DIY

What was the problem - and did changing the BLS fix it? 2008 MY Java Black TDV8 HSE

My TVR's had their problems but great fun and never caught fire. Hoping my RRS will give me as much pleasure, very enjoyable so far. My problem was a very intermittent suspension warning light which my indie did not think was anything serious after a couple of checks with his computer. On a long trip tomorrow so will be giving my efforts a good test and will post results.  past personal chariots
TVR S1, TVR Chimaera, Mercedes 500SL, all sadly missed but age demanded easier access.

After changing the brake light switch the suspension warning light came on as soon as I started driving, I tried restarting a few times, a restart used to eliminate the light, but the light persisted in coming on. I had a 400 mile journey to make so bit the bullet and went. Nothing untoward and the journey completed at 19.9 mpg at a smidge over 70 in a 4.2 SC which I was happy with. The next day a few local trips and the light stayed out, as it did the day after with a 150 mile trip followed by 250 miles towing a caravan and then the light came on again but out after a restart for the next 50 miles home. The only other incident happened close to home when the engine warning light blinked followed by a power reduction, I assumed limp home mode. After a restart it was back to normal. My question now is do I ignore intermittent warning lights which go out after a restart with no other signs of malfunction and just treat them as an irritation or have the problem investigated by the professionals. My inclination is to physically check what I can, visual inspection, fluid levels, tyre pressure, vehicle posture etc and only go further if a warning light stays on continuously. Comments gratefully received by a newbie.  past personal chariots
TVR S1, TVR Chimaera, Mercedes 500SL, all sadly missed but age demanded easier access.