Just did a quick search for surface mount diodes with the JA marking - a number came up:

I think Jag is using a similar package and paralleling the diodes for increased current capability:

Example:

Notice where it says "marking" BAV74 JA

 

Yep, that seems to be the Puppy.
Everywhere I look they are right around 25 cents.... PLUS $3 - 10 shipping.
Guess I go to Radio Shack and buy a Normal Diode for a nickel and see if it works.
Going by the circuit and the PCB, a single larger diode should do exactly what that tiny one does. And it is SERIOUSLY tiny. 1mm X 2.5mm

 

A regular diode will work fine CJ.

 

A trip to RS and $2 for two diodes, a few minutes soldering and VOILA; Working CHMSL.
Now I'm glad my local Jag dealer never replied to my inquiries for a new harness. Probably would have been $722.

 

Right on.........

I think you should change your profile pic to this CJ;

 

In my younger days I could have designed a morse code strobe for the thing and built it out of water heater parts. *sigh* I can't even remember ONE of the color codes for resistors now. Age really sucks.

 

I've got the color code burned into my brain after years of looking for resistors in cheap mixed bags...my eyes were much better then.

Where is the board located in the car by the way - it may come in handy to know for the future.

 

Inside the trunk (boot) lid behind the interior panel. It's directly to the left of the FM Signal Amp and connected to the tail of the CHMSL array. The whole thing seriously is less than a foot long from F-conn to M-conn, with 22 gauge wires.

 

Get it fixed? I had the same issue with my XKRS; different 3rd brake light but the failure was in the short removable harness (not sold separately). The shop I had it at sourced failed "diode" @ local electronics place in Calgary and they fixed it by soldering in new part. I do not know which item in your photo was the culprit but if I can help, let me know. Could hook you up with name of shop.

 

Yes,I fixed it. I desoldered that "JAY" deal, then soldered a 12V diode in its place. Everything works wonderfully now. Cost me a buck.

 

Well done Cee Jay!
So you've still got Radio Shack in your area? They all disappeared from mine a couple of years ago, and I assumed they were totally out of business.

 

I have one left in a forty mile radius when there used to be seven or more. One was just over a mile from me, now closed. The only one close is now 15 miles.

 

Yep, used to have one just over a mile from my house as well, and I walked right by the front door twice a day as I walked to and from work. I guess that was part of the problem, I walked right by, rarely ever stopped in, and when I did it was for a small $ purchase, the big stuff I bought elsewhere.
The most I ever bought there was when the store was closing, and I was grabbing as much as I could at 75% off, kind of sad.

 

OK, bump outta nowhere.

9W83-18K891-BA = C2P20329, parts catalogue calls it "antenna, high mounted stop lamp, positive, radio"

But that is not the Suppressor shown in the wiring diagram paralleled with the high mount stop light, those are p/n C2C41321 or C2C10805.

This part is also used as a noise suppressor in the ignition system in the X350 XJ, the S-Type, and also the XK, under the bonnet.
These suckers;



In the XK they are also in the left side of the boot, if you pop out the plastic vent panel you will see it. I've been going through this hell the last few days with my radio reception crapping out...

But for the life of me I have not found this 9W83-18K891-BA / C2P20329 inline in the cable to the centre brake light...

 

According to the wiring diagram, it is connected in parallel, not in series. It splits off from the brown/red feed to the stoplight at connector CA054 (LH rear), and then connects to ground.

 

Yeah, this one



Is the one in parallel to the brake light.

It's not the one in CeeJays pictures, I can't find that one.

 

Durrr - that will teach me not to post before reading the entire thread...

It's because they changed the design. The earlier type is the parallel unit we've been discussing. There's a later one, which I've now found in the diagram for VIN 44940 onwards:

 

Is that boxy thing openable to attempt a fix?

 

Most things are openable, given the application of sufficient impact engineering...

 

On AF aircraft, components like that are filled with "potting compound", a catalyzed goop that completely engulfed the entire circuitry to 100% eliminate any possibility of component movement or environmental contamination. The stuff was nearly impossible to remove. If attempted, the circuitry was destroyed anyway.