I had the usual Cruise Control Not Available, Check Rear Lights message on and off over the last driving season until I put the car away (2004 XK8), last fall.
It had gone from intermittent last summer to steady by fall so during the winter I took out the switch. The micro switches clicked nice and crisply and a continuity check show they were functioning. Rather that order the switch right off I tried re-soldering the circuit board and spraying contact cleaner in the wire harness connector. I can't be sure which procedure cured the problem but I have now been driving the car for a month and the issue seems to be fixed. I hope I haven't jinxed anything writing this. Picture included of what I re-soldered.



I re-soldered all ten of theses connections with a pencil iron.

 

Well done. An EE buddy of mine fit new switches and did the circuit board re-soldering to a couple of my old brake pedal switch assemblies back in late 2016. One is installed in the car (and performing normally) and I keep the other on my garage shelf as a spare. As much a contortionist hassle as it is to remove and install these switch assemblies, it is truly a shame that they were built so poorly....

 

I failed to reset the white plastic self adjuster the first time I put the switch back in, so I got to do the contortionist position twice. As far as your comment on so badly built, I think that I kind of expect some things to fail on a 15 year old car with 193,000 km. I am in automotive quality and am often required to validate life cycle tests. I think my Jaguar has certainly surpassed many of the validation tests that many modern cars are required to meet.

 

That may be, but keep in mind that some of these brake pedal switch assemblies began failing at only four or five years old with less than 40,000 miles on them....

 

I just called the dealer for "fun" to see what they charge. I have the part. $420 plus tax. so guess what I'll be doing.

 

That should just about cover the labor for their on-staff circus contortionist....

 

This appears to be similar to the problem with the ABS circuit board, where there was a solder joint that went bad. I'm sure they corrected these issues, but they seem common. I sort of wish I had known to do this fix instead of just replacing the switch. It's probably better in the long run.

 

Now that's my laugh of the day. Thanks.

 

My 11 year old daughter wants to help me do this job. The only part I'm having trouble with is, after the switch is out, as she feeds the switch into place to the firewall, must we depress the brake pedal so the switch slips into the proper area? I've read many threads on this, and don't want to start beating a dead horse, but I want to explain it right. We are using the fishing line method on the studs for the old switch then attaching them to the new one. My fat head won't even fit under there

 

It's much easier to remove the switch from the mounting bracket. The top nut just has to be backed off a little. I also backed off the nuts in the engine bay to make it easier to get the switch over the rod on the pedal.

 

R3Wood,

Yes indeed, your daughter needs to depress the brake pedal as she lays on her back and feeds the new switch assembly up into place. It will all make sense once she is down there in position. I believe my wife used the back of her head (or maybe it was the back of her shoulder) to depress the brake pedal on both occasions we had to replace her switch assembly. Good idea to get a kid to handle the contortionist part of the job. Be sure to take her out for ice cream in the car after you're done....

 

Thanks. We did see how the switch seems to work backwards, push pedal down, the switch is free. This may be one of the dumbest things I've seen designed . We had no luck last night, we are using the stick now. We actually got one in but I think we ended up getting the top bracket stud on the bottom hole. Then more fun as I dropped the nut down into the area underneath. LOL. I spend a lot of time lifting weights and my dumb *** chest would not even fit under the steering wheel when all the way up.
It is frustrating, but I think today is a new day . My daughter is in great shape from sports and even she had trouble staying under there for too long. I looked at taking the seat out but none of torx fit. Will do on the ice cream.

 

Thanks RJ. I committed to the dumb way

 

Get the correct Torx bit (a T-40 fits my wife's 2006 XK8) and take the seat out. Even though your daughter is young, thin, and flexible, removing the seat will give her so much more room to position herself properly which will make it easier for her to align the two studs up into their mounting holes. Be sure to run the fishing line down through the mounting holes and tie them to the studs before you start the job. You can then pull steadily on both lines while she guides the assembly up into its correct position. Have your daughter look at how the assembly fits into place BEFORE she crawls down there on her back. Then remind her that because she is on her back and looking up, guiding the two studs into their proper holes is all about reverse thinking on her part - up is down and down is up. Help her by keeping the lines taut with your steady pull. This approach really worked for my wife the second time we had to perform this fix on her car....

 

Thx Jon will do. All tips are good tips.

 

 

Well done. Be sure to keep your faulty brake pedal switch assembly and think about replacing just the two microswitches so you will have a spare on hand when the new one decides to get flaky....

 

 

Hi Everyone,
I am new to this thread.

I bought a brand new OEM Brake Light Switch from Amazon. Installed it (following the great tips from folks who has done it) but the dual msg "cruise not available" & "check rear lights" return.

I was able to verify the brake light switch is indeed NOT defective, that is the 2 outer pins are normally in closed circuit (resistance is near zero); the 2 inner pins are normally in open circuit (no resistance)

Now I am really struggling what is going wrong here. I have checked all the rear light bulbs and connections. They all seem OK.
I also noticed that the dual msg usually will show up soon after I applied the brake a few times regardless of how far or how fast you travel.
If I stop and re-start the engine, the dual msg will clear until the next cycle.
It is intermittent but very predictable.

Does anyone has similar experience and how you go about to fix it? The re-soldering of the wires seem very interesting to me, but again I am very puzzled as to why a supposedly new and non-defective brake light switch doesn't solve the problem??

Thanks for sharing