XK8 Brake light switch repair guide
Junior Member
Joined: Jul 2018
Posts: 13
Likes: 4
From: 94546
Hi RJ237, thank you for your insightful information.
I was able to verify the continuity of the 2 circuits with the pedal depressed is correct and as expected.
Upon dis-assembled the brake light switch assembly and physically inspect the 2 microswitches, I can see and feel that the spring on one of the microswitch has more play than the other. it certainly has worn out some compared to the other one. Now I believe this is the root cause of the problem. That is the spring rate of the 2 microswitches is no longer the same. So when the brake pedal is depressed, on some occasions, the 2 springs of the microswitch do not work in unison.
I was able to verify the continuity of the 2 circuits with the pedal depressed is correct and as expected.
Upon dis-assembled the brake light switch assembly and physically inspect the 2 microswitches, I can see and feel that the spring on one of the microswitch has more play than the other. it certainly has worn out some compared to the other one. Now I believe this is the root cause of the problem. That is the spring rate of the 2 microswitches is no longer the same. So when the brake pedal is depressed, on some occasions, the 2 springs of the microswitch do not work in unison.
Revise guide for LHF6420DA 1996-1997 MetalBracket version can be repaired with:
2x RS # 560-574 (DIN 7885 - M2.5x20) Bolts
2x RS # 560-287 (DIN 934 M2.5x6M) Nuts
2x RS # 320-512 (Cherry DC1C-C3LC) Microswitches
Black - Gray = Opening contact
Black - Blue = Closing contact
Your welcome,
Tomi
Veteran Member
Joined: Feb 2012
Posts: 1,114
Likes: 567
From: Portsmouth, England
I would suggest that many of the intermittent problems with the brake switches are the result of dry solder connections where the switches are attached to the small circuit board.
That was my experience and since re-soldering the original (apparently) wayward switches I've had many thousands of trouble free miles.
That was my experience and since re-soldering the original (apparently) wayward switches I've had many thousands of trouble free miles.
Member
Joined: May 2017
Posts: 82
Likes: 6
From: Michigan
I replaced the switch on mine as well, but did not want to go through the nightmare bracket replacement. I had read about this method of replacing the electronics only, and in less than 5 minutes, I had replaced my Brake Switch Electronics, start to finish.
1.) Place hand mirror on floorboard.
2.) Sitting on ground next to vehicle, reach up and bend the bracket toward the Passenger door ~1.5"s, while holding the brake pedal down to clear the Brake Pedal Lever, the bracket will bend very easily, do not push hard.
3.) Remove bottom nut with small Ratchet and Socket, clip tie wrap and disconnect harness, lift electronics over nut post on bottom of bracket and swing ~15-30 degrees to the side to clear the bracket and pull electronics off, no need to loosen the top nut.
4.) Install new electronics to old bracket in reverse, paying attention to the plastic washer at the top, and bend bracket back straight while holding brake pedal down so the lever clears the switch in the electronics, re-connect harness.
This is how I replaced my Brake Light Switch, I encountered no problems and the CC works every time, and like I said, it took 5 minutes. The mirror on the floorboard allows you to see everything that you are doing.
1.) Place hand mirror on floorboard.
2.) Sitting on ground next to vehicle, reach up and bend the bracket toward the Passenger door ~1.5"s, while holding the brake pedal down to clear the Brake Pedal Lever, the bracket will bend very easily, do not push hard.
3.) Remove bottom nut with small Ratchet and Socket, clip tie wrap and disconnect harness, lift electronics over nut post on bottom of bracket and swing ~15-30 degrees to the side to clear the bracket and pull electronics off, no need to loosen the top nut.
4.) Install new electronics to old bracket in reverse, paying attention to the plastic washer at the top, and bend bracket back straight while holding brake pedal down so the lever clears the switch in the electronics, re-connect harness.
This is how I replaced my Brake Light Switch, I encountered no problems and the CC works every time, and like I said, it took 5 minutes. The mirror on the floorboard allows you to see everything that you are doing.
Great post, BTW...….best explanation that I have seen.
Senior Member
Joined: May 2011
Posts: 106
Likes: 43
From: Texas
Fixed mine usimg 03xkr method
Fixed mine today using 03xkr's method but I did the contortion thing rather than the mirror method.
I loosened the top nut and now I can't tighten it - is it important?
The Omron switches were in stock at Digi Key
I loosened the top nut and now I can't tighten it - is it important?
The Omron switches were in stock at Digi Key
Veteran Member
Joined: Dec 2016
Posts: 1,323
Likes: 483
From: S.W.Florida
Hi guys. I have just dialed into this thread and been reading your journey. I just picked up a 2006 XK with this problem and will be having to replace this switch. Does anyone know if these switches are still available, and where they can be sourced(Amazon?). Glad to see someone has sorted out the process of how to most easily replace these things.
Junior Member
Joined: Nov 2013
Posts: 26
Likes: 12
From: MD
SamtheSham, based on the posts from marcgr and racediagnostics that preceded yours, the replacement microswitch mentioned is readily available for $3.42 from
https://www.digikey.com/product-deta...152-ND/1811813
Another option is replacing the whole switch & bracket assembly if you're so inclined. Rock Auto shows two left in stock at $104.79 (p/n SLS503), a considerable discount from the dealer price.
https://www.rockauto.com/en/moreinfo...689531&jsn=258
https://www.digikey.com/product-deta...152-ND/1811813
Another option is replacing the whole switch & bracket assembly if you're so inclined. Rock Auto shows two left in stock at $104.79 (p/n SLS503), a considerable discount from the dealer price.
https://www.rockauto.com/en/moreinfo...689531&jsn=258
Last edited by flat6; Jun 29, 2019 at 07:27 PM.
Veteran Member
Joined: Jan 2009
Posts: 13,076
Likes: 4,724
From: Raleigh, NC
Replace the two original microswitches on the circuit board with far better ones rather than ordering a new brake pedal switch assembly. If you opt to install a new assembly, you will eventually be doing the job again when it fails. Ask me how I know....
Senior Member
Joined: Mar 2015
Posts: 174
Likes: 33
From: Australia
Repaired mine using two microswitches costing less than AUS$10 plus I paid an autoelectrician AUS$20 to change the switches as my soldering iron didn't want to melt the solder on the old switches. An absolute bugger to replace the switch and only succeeded when I used two fishing line attachments to the mounting studs plus my wife's help watching for the studs to appear under the bonnet (hood) while keeping tension on the fishing lines.
Many thanks to all who provided valuable advice.
Many thanks to all who provided valuable advice.
Veteran Member
Joined: Dec 2016
Posts: 1,323
Likes: 483
From: S.W.Florida
I(and my friendly mechanic) have replaced the entire switch twice). Still keep getting the msg. Traced out the circuits, checked all connections, all brake lights, all work as expected. I went into the manual found fuse #22 under the hood(bonnet) listed as the "integrated cruise control". Pulled this out to see what effect this would have. When the msg was still out, the cruise control still worked?? Once I replaced the fuse was replaced, now I got the msg, "Cruse control canceled".
I can live without the C.C. if need be, but this is beginning to become very confusing.
Anyone have any more ideas??
I can live without the C.C. if need be, but this is beginning to become very confusing.
Anyone have any more ideas??
Senior Member
Joined: Oct 2017
Posts: 213
Likes: 46
From: Sarasota
Hey Guys,
Wondering if you could provide some guidance. I have been getting the Check Rear Lights/Cruise Not Available warning so I figured my brake switch has failed again. I actually have the old switch along with another supposedly bad in the garage. I figured I would switch out the microswitches to put two good switches on one unit and then replace it. I brought out the multimeter and set it to ohms to test the continuity. It is so strange, on both units, the outside pins are closed and then when I hit the microswitch they go open and the inside pins are open and when I hit that respective microswitch they close. Does this make any sense to you guys? I thought that both of these brake switches were defective and one of them actually did come from my XKR a year or two ago when it was flashing the warning. Perhaps they fail after warming up or something?
Thanks,
Coery
Wondering if you could provide some guidance. I have been getting the Check Rear Lights/Cruise Not Available warning so I figured my brake switch has failed again. I actually have the old switch along with another supposedly bad in the garage. I figured I would switch out the microswitches to put two good switches on one unit and then replace it. I brought out the multimeter and set it to ohms to test the continuity. It is so strange, on both units, the outside pins are closed and then when I hit the microswitch they go open and the inside pins are open and when I hit that respective microswitch they close. Does this make any sense to you guys? I thought that both of these brake switches were defective and one of them actually did come from my XKR a year or two ago when it was flashing the warning. Perhaps they fail after warming up or something?
Thanks,
Coery
Senior Member
Joined: Oct 2010
Posts: 748
Likes: 308
From: Near Charlotte, NC
Senior Member
Joined: Oct 2017
Posts: 213
Likes: 46
From: Sarasota
Thanks for the reply. I do understand how the switches work but what I do not understand is how my supposedly "faulty" switches are testing this way. I would have thought that when I test the pins on these units they would not show such promising results.
Senior Member
Joined: Oct 2010
Posts: 748
Likes: 308
From: Near Charlotte, NC
I cannot explain this mystery either. I do know that having checked the switches for continuity and the board for bad solder joints to no avail, I bit the bullet and went with new microswitches which are still proving to be successful . Here is my post #5 from another thread posting such:
https://www.jaguarforums.com/forum/x...3/#post2168245
a brake switch
hello, same problem with 2006 xkr. I took a switch assembly apart and tested with Ohmmeter and they worked. I re-soldered all points. I do not have any power going to switches. Do they connect ground? All fuses are OK. What switch releases the shifter solenoid?
I removed the switch assembly, tested microswitches with Ohm meter and they seem to be working. I connected them back to the harness, but no change. Just opposite - Now I am getting warnings : Electrical fault, suspension fault, handbrake on, All fuses are OK. Where I should look. Is the body ECM fried? Some hints, please.
I removed the switch assembly, tested microswitches with Ohm meter and they seem to be working. I connected them back to the harness, but no change. Just opposite - Now I am getting warnings : Electrical fault, suspension fault, handbrake on, All fuses are OK. Where I should look. Is the body ECM fried? Some hints, please.
Last edited by dneu; Jul 11, 2020 at 02:33 PM. Reason: more problems
Junior Member
Joined: Mar 2022
Posts: 1
Likes: 0
From: Harpenden
98 XK8
Im finding it difficult to purchase a brake light switch for my 98 XK8.
Does anyone know if I can use a switch for a xj - they look exactly the same? They have the same code - LJB6420BB
Thanks,
Neil
Does anyone know if I can use a switch for a xj - they look exactly the same? They have the same code - LJB6420BB
Thanks,
Neil
Junior Member
Joined: Oct 2017
Posts: 19
Likes: 1
From: Hoschton, GA
Dan