Background: past couple of days I've gotten rear bulb failure when cold and first few applications of brake. Clears itself after a second, does not occur for rest of ride.

Today I did surgery on turn signal stalk connections. Required disassembly of lower valence, upper and lower cowl on steering column.

Put all back together, started her up, very cold outside. Press on brake to shift out of park.

Immediately saw bulb failure message, but at same time and for first time ever heard solenoid click to unlock shifter.

Once again bulb failure message went away in a second or two, but still I hear solenoid click.

Here's my question:

Are either of the two brake switches low enough on the brake pedal so that I may have restricted it's movements with a misplaced wire during assembly?

Should I be concerned about suddenly hearing the solenoid or should I just write it off to cold weather performance?

I'll check the rear bulb connections tomorrow but I wouldn't be surprised if the switch is going bad.

Thanks for your thoughts. John

 

What we generally know about this particular failure is that one or both of the microswitches on the circuit board begin to wear out and cause intermittent messages to appear that alternate between "check rear lights" and "cruise not available". When I've driven the car while this was taking place (once for 125 miles at a stretch), I've never heard the solenoid clicking. But then again, I wasn't listening for it....

 

Thanks Jon, I never heard it before either. Frankly I'm probably being paranoid. It was 30 degrees out, and I can't think of anything I could have done that would increase the sound of the bloody solinoid.

I sure do wonder about the intermittent bulb failure message. It seems to me that a failing switch (delay sending a signal to the BPM) would not be an intermittent display. Thinking about how these error messages display - if there's a particular error they pretty much stay displayed until you recycle the ingnition or something. I wonder if I'm about to find that a failing switch shows the error message until ignition is cycled off/on, whereas the a bad bulb connection only displays as long as that issue is present.

Wondering out loud: As I recall there are 2 switches on 1998s. One for brake lights, the other for cruise control. If they don't fire simultaniously it creates an error condition. Not sure what message gets displayed here or how long it lasts for. Maybe someone knows that is the loss of cruise control message?

OTOH if a brake bulb is faulty, open or bad connection, that's going to display bulb failure rear.

Logic says that the brief error message display points to a bad bulb. Well as you can tell this is my first battle with this condition. Just wanted to bounce it off you in case someone might know a bit more about this.

Thanks,

John

 

Generally a failing brake light switch produces "cruise not available" and will not unlock the shifter when the brake pedal is depressed.
The rear bulb failure is a common problem for the early XK8's. If you do a forum search for "rear bulb failure" you will find write ups for adding an additional ground wire to the rear light assemblies.

First do a couple inspections. Unplug the connector going to the rear light assembly and examine the plug on the wire side. It should contain a row of fingers pointing at each other and they should all be uniformly spaced. If any are bent away it is from heat and they can be pushed back into line. Also, check the connector point at the end of the plug is it showing signs of heat distortion at the prongs or the plastic?

Your post did not say when this is happening. Is it when you first start the car. If so does it go away and not recur if you shut the car off and restart. If that is happening then you need a new battery.

Take a look a the things suggested and get back to us.

 

SOLVED!!! I cleaned all the bulb connections, all looked good. Took her for a test drive, all good until the last minute when I pulled into my driveway and put her in reverse = Bulb Failure message.

Well this was good news I could capture this. Turned out that I could turn ignition off, wedge the break pedal down, put on e brake and take a look in the rear.

Sure enough 2 lights were out on the left side. I pulled the bulb assembly back and looked harder. Funny thing - if I unpluged one, the other would light! Wasn't long til it gave itself away: The Ground pin started smoking!!! (gotta love it when the answer stares you in the face)

Didn't take me long to find Brutal's fix, soldering in a proper sized ground wire to the circuit plane, then attaching to the body with the nut holding the lamp in place.

Guys this was the fastest job I ever completed on the Jag. It couldn't have taken more than a few minutes.

It all made sense, brake depressed + rear back up lights overwhelmed ground - failure message. This job was so easy I probably should have just done it years ago. I am going to do the other side tomorrow.

John