I bought my XKR X100 2005 with the following faults and parts supplied to remedy. Sadly, the previous owner has passed away but said something about the location being near the brake pedal and being difficult to access.
Haven’t found any relevant threads yet. Can anyone shed any light at all on better identification of the fault and solution? Thanks.


The reported faults

The part numbers

The switches requiring fitting

 

Doesn't the advisory refer to fluctuations on the brake test roller? That would lead me to look at disks and pads.

 

I thought it referred to a fault indicator-light flickering inside the car. The previous owner was an engineer with JL, so, I assume the switches are the correct cure but to what? If I can’t sort, i’ll find out more when it comes up again at the next MOT! Thank you.

 

What is being talked about is the infamous brake/cruise control switch. It manifests by showing something to the effect of "cruise control unavailable - check rear bulbs" after driving a while, if memory serves. The "switch" is really an assembly with a trigger activated by the brake pedal stem and a pair of these micro-switches, one wired normally-open and the other normally-closed. The control module checks that these switch are in opposite status and returns that message when they are not. The fix is either a new assembly for $$, or replacing (basic soldering skills involved here) the micro switches themselves on the circuit board for much cheaper. There are may posts about this, this is a common problem.

Part of the difficulty is to reach/remove/reinstall this switch assembly. It is located in the driver wheel well, above the brake pedal. Some remove the seat for better access. The switch can be removed from its bracket (2 small nuts involved, the top one only needs to be loosened) or with the bracket. The bracket screws are in the engine compartment by the brake booster. Challenge is to have the studs on the bracket align with the corresponding holes on re-assembly. Expect nothing but pain and frustration, but, then again, some go in this with a healthy dose of beginner's luck and get it done in 30 min.

Not sure how your reported faults relate to this, but this is what the common problem is and what those micro switches are for.

Best of luck, keep us posted.

 

My detailed BPPS (Brake Pedal Position Switch) write-up and pics in X308 forum, shows the micro-switches. Search "Brake Pedal Position Switch (BPPS) on X308 Sport." Yes, the X100 uses same layout and the R&R is a real pita. If you go from below, removing driver's seat makes the job doable, but you need patience and dexterity!

A timely hint for others . . . the same micro-switches can be bought at any good electronic parts retailer for about $2 each. Just ensure that you purchase ones that have the same actuating arm, as there are several varieties built on the same body mechanism.

Cheers,

 

I disagree. The advisory is ref 1.2.1 (e) for the offside front and offside rear brakes, which is in the MOT handbook as:

(e) Excessive fluctuation in brake effort through each wheel revolution

That's nothing to do with a brake switch, and the parts you have been provided have nothing to do with that advisory. See here for info: https://www.gov.uk/guidance/mot-insp...#section-1-2-1

Apart from anything, there is no way for a warning light to be attributed to a particular wheel!

 

This ↑

What the advisory refers to here is a fluctuation in braking effort at the wheels during testing. It's nothing to do with switches or lights.
EDIT:- I wouldn't wait a year till the next MOT to see what's what (or gotten worse). These are your brakes & you want them working properly, esp. in Argyll during the Winter.

 

Thanks for all your advice. It is very helpful. The brake pedal/cruise thread certainly relates to something the previous owner said. I’ll address that soon. The car is due for re- mot right now having just completed failure items of rear subframe and front bushes/ball joints. This will help me home in on the true nature of these advisories. The disks and pads are fine and any suggestion that this advisory is detrimental to braking would surely have resulted in it being a major defect? Anyway, onwards and upwards. All responses very much appreciated.

 

I have to say, I do find it odd that both offside wheels had the same advisory. You'd normally expect this sort of problem to be due to a warped disk, or something like that, and to have the front and rears with the same issue feels rather unlikely, so I do wonder if there was a problem with the brake test roller. But if you're having it tasted again (assuming it's a different place?) you'll get a view on that when they put it on the roller.

 

Not so. There are limits as to what's acceptable (& if there were nothing wrong, wouldn't have been noted as an advisory).

Good luck with your car.