Hi , new member , first post. I have a 1997 XK8 coupe where the brake lights work fine, but it won't let me get out of park. (I currently have the console off and operate the solenoid manually.) It seems this brake switch is my next place to check. Car has done 157k KM . Is this switch capable of being dismantled and cleaned (and is it worth doing?) or is it sealed ? My car ( Australia) is RHD and this switch is on the RHS of the column and very difficult to access...so I'd really like to get it right first time if possible. Thanks for the help. Cheers !
PH

 

Hi Peter,

If your brake light is operating on and off with the brake pedal, then the brake light switch seems to be working. Its purpose is to both activate the light and (probably indirectly through a control unit) activate the solenoid. I would suggest, before you look at the switch, you perform some tests on the solenoid and it's power source.

Answering your question: The brake light switch can be dissasembled easily by removing two nuts. Inside is a microswitch and a cam. The microswitch can be oiled (WD40) but probably will need replaceing if it is faulty.

Tom

 

Peter,
The unit could be disassembled and cleaned however the likelihood that it would act up again is very good. I believe that when I changed my switch it was double sided, one for lights-one for park release, but it has been awhile ago. Chances are good that the side that controls the interlock is not working and the light side is.

Charles

 

Yes... From reading "everywhere" I don't think the fact that the brake lights work is an indication the switch is totally OK. I can see my switch plug has four wires which (normally) would mean two sets of contacts. I think (stress THINK) one set is N/O and closes to operate the brake lights ... and the other set is N/C and opens to "talk" to the ECM ( according to Fig 05.2 of the JTIS ). It would make sense that the N/C set "sticks" as they would be held closed for 100% of the time ...except when the brake pedal is actually being depressed.
PH

 

My 1998 UK XK8 only used two of the pins. I opened it while waiting for the replacement to be delivered. Kind of kicked myself after I managed to fix it with a £1.50 microswitch from Maplin. Could have saved myself £60 on replacing the complete switch. Still, I know I have a quality component and not something that could be unreliable.

By the way, if you want an easy way to put the switch back on the car use you head. Literaly, that is, to hold the brake pedal down and looking up you should see one of the holes for locating the switch. Bet you get it back in first try.

 

Hi Tom, did you remove the driver's seat ? Just interested. Please send photo of you "adopting the position"!! I'm struggling with this one. I'm referring to the JTIS wiring schematics. The brake sw. for the gearshift interlock sol'd is shown on Fig 05.2 - The brake switch for the rear brake lights is shown on Fig 09.2 - Since the connector/pin number are the same AC24-1 & AC24-4 on each Fig this would mean it's the same switch/contacts that perform both functions. So, if the brake lights are working, that means the switch contacts are operating correctly. Both Fig's then direct me to Fig 02.1 and Switched Ground "7" ..which according to Fig 02.1 is wired to the ign. switch. Once again, since the brake lights work with the ign "on" , this means all that circuitry is working OK. Have I got my thinking straight on that ?

So in terms on my interlock sol'd not operating, where next should I look? The sol'd has two wires - one wire grounded and I have checked that ground is good with multi-meter. When I jump on the brake pedal with the ign "on" the other wire to the sol'd has no volts. According to the Data sheet for Fig 05.2 we should get B+ (which I guess is 12vDC) out of the Body Processor Module. It would appear there is no relay involved.

All advice greatly appreciated. (...and needed. I'm not as flexible as Tom.)

 

Hi Peter,

Find a sheila that will allow you to put the "adopted position" on this forum .

It sounds like you are looking in the right place with the solenoid. If you measure the voltage across the solenoid's connectors, of course it should change with the pedal. Since it isn't, it sounds like the power source is the problem (module or wire failure). Personally, my next step would be to take off the solenoid and test it in isolation with my own 12v power supply.

 

Hi Tom, Still lookin' for accomodating shiela ....but solenoid is out of car and tests OK. Resistance is about 46 ohms measured by DMM. No sign of any grounds. Bench test on 12V works perfectly for as many cycles as I like. No sign of any sparks when you bench test so current draw must be pretty low. All looks OK. If you remove this solenoid, be warned there is a fine spring behind the plunger. Easily dropped & lost etc. The sol'd has a Lucas label so you can feel the ol' Prince of Darkness waiting to pounce. To remove the sol'd, just remove the five nuts that hold the j-gate assembly (at the base) in place, then two nuts that hold the sol'd. Pretty straightforward with the console apart.

Next step seems to be check wiring from sol'd back to module. Does anybody have any tips or experience with this wire? Thanks

 

Peter, I have been scouring the forum for info on the brake transmission lockout issue, as mine is intermittent, it sometimes takes three or four key cycles/brake depressions to move out of park. I appreciate any other info you or others have found on this issue.
Thank you!

 

Weeb, Since you car is also '97 maybe I can help. Couple of checks. (1) IF your brake lights work CONSISTENTLY every time, then (I THINK) that means your brake switch is OK. Do they ? (2) Does your car make a warning sound (mine is repeated quick beeps) if you try to move the shifter out of park ...with the ign OFF and no foot on brake? Does it do this also CONSISTENTLY ? If so, (I THINK) this means your "park"position micro-switch is OK. Let us know.

 

Thanks, Peter! The brake lights work consistently except long night drives, and then the turn signals give me the "bulb failure" warning intermittently as well, so I strongly suspect that those issues are related to the tail light module grounding problem (many bulbs running hot thru that tiny ground tab).

Very cool check on the warning sound, just tried it a few times, yes, I get the triple beep when I try and move the shift out of park as described. So, I will now search the forum for info on the brake lockout solenoid (assumption) itself. Not that it might be related, but I also have to fool around with the J gate when going from drive to reverse and back; usually have to go past reverse and then back to the notch for it to go into reverse.

 

Weeb, I'm not experienced on the "relationship" between your turn signals and your brake lights. All I do know is if your brake lights work CONSISTENTLY then your brake switch (up under the dash) is OK.

Your "need to fiddle" with the J-gate between D and R almost certainly is to do with your Neutral position micro-switch. (You pass through the N position between D and R each way). This micro switch is the most attrocius engineering. Mine had the (TINY, TINY) lever broken off . The lever was down in the j-gate. The lever hinges on two TINY plastic "****". IT IS BAD ! Also beware, if you look, the j-gate top plate has a "bump" around N and it seems to me this is to protect that N position micro switch. With the j-gate top removed, it would be SO easy to bust that switch when you move the gear shift. If your switch is busted AND you can find the tiny lever, I drilled out the hinge point right through the switch ( there is enough "meat") and placed a small nail so that it became the (metal) hinge. Mine works a treat !

 

My park interlock solenoid is on the bench and tests perfectly. See previous post. Now I tested the voltage at the two pins in the connector that connects to the sol'd. (Paper clips are just the right diameter to get in the holes.) With the ign ON or OFF, I get 7.76V constant at the pins no matter what I do ! If I start the engine I get 8.3V. Punching the brakes does nothing ( I can see the brake lights come on so the switch is OK.) I switch the ign off and the 8.3V remains. The only way I can get "rid" of the 8.3 volts is to disconnect the battery. When I then reconnect the battery it's back again. If anybody can tell me where to go next in this saga, I'd really appreciate the help. Do these computer modules use a "sensing voltage" or something ? When I read the "books" they seem to stress that "all components" need to be "connected" ..in which case how do you test anything ?

 

Hi you blokes... see my last post. I'm stuck and need help. I'm bumping this thread .... maybe we're a bit off thread anyway. If no response I'll start a new thread dealing with the ign. park interlock soldenoid in particular ... I guess.

 

Great info. Do you know if a 2001 VDP brake switch has the same position and replacement directions you gave? I understand putting the new switch in is a bear. Any advise on positioning new switch bolts?

 

SgtofMarines1775,
Thanks for a great write up. Made the job very easy, even for an old retire Msgt of Marines! Semper FI.

 

We just replaced mine. This is a definitely a two person job. My wife used her yoga moves to get up into the well. No way I could get on my back up there and find those holes.

In this situation, the symptoms for replacement of the switch were a little different.

The dash screen was showing an "ENGINE FAULT" script; but there was NO "Check Engine" light. This occurred only when the Cruise Control button was activated. The cruise control was inoperable under these conditions.

Apparently, the second set of the four (4) brake pedal switch contacts goes to the Cruise Control [via the ECU]. This is to deactivate CC when the brakes are applied. When this functionality is not working, because of a faulty brake pedal switch, the ECU deactivates the CC. Why the ECU presents this as an Engine Fault warning is beyond me, but that is the symptom presented.

 

Gordo,

Good to see you on line. I see the xk8 was misbehaving for you. What’s with that?

 

Hi Gus... I was offline for a few weeks recovering from open heart surgery in August. My aortic valve was replaced. Both my parents had similar problems; and I grew up knowing I might have the same fate. So it was no great surprise coming as it did.

I am near fully recovered now. Actually today I was beginning to jog again on the beach. Such a wonderful feeling.

 

I did not know but am pleased you are doing well. I have been waiting for the heart problem after being exposed to Agent Orange. So far I have been lucky. Whatever you do don’t let it beat you!