A local mechanic recently replaced my passenger side brake light. The high mount stop light (HMSL) immediately stopped working. The mechanic refused to sign the brake light repair order because of the inoperable HMSL.

I suspect there is a broken fuse but can't find any mention of its location in the X-Type owner's handbook. Does anyone know the fuse location?

Could there be a broken wire back by the passenger side brake light?

 

Raven2016, first off, welcome to the Forums. There are a lot of people here willing to help you out. But, we ask 1 thing in return. Please stop by the New Member Section and introduce yourself. tell us a little bit about yourself and what got you into Jags. This will also help you get to learn who the key people around here are too. We also pride ourselves in being a better car group and I think once you see what this place offers, you will see why so many stick around here even after getting rid of their jags.

Now, for your problem, you need to realize that you have the possibility of 3 different wiring harnesses in your car (pre March 2004, Post March 2004, and 2007+). So, please, give us the year of your car (if a 2004, look in the driver's door jam and give the month/year the car was built, it is posted there). The other potential variation here is whether you have the standard sedan or if you have the station wagon (sport brake) version. The wagon versions are fairly rare, but does change things.

Now, I am going to go out on a limb and make a few assumptions about your car and we'll see where this leads us. I am going to assume you have a late 2004-2007 standard sedan. With this being said, if your tail lights are still working (ie, they light up when you step on the brakes), then we know the fuse to the 3rd brake light is good (shares the same fuse as the normal stop lights). This also proves your brake switch is good too. If all this is true, then I need you to look at the plug to your passenger side rear lights. If you look at the plug, at post #5, do you see an orange wire and an orange wire with a green stripe there? Or, do you see something else (single orange wire or possibly an orange wire with a red stripe)?

Thinking about what work has been done, I am placing money that you may be seeing your brake lights working, but there are other lights coming on too that shouldn't be. A common problem with the X-TYpes is that people do not install the correct bulb and/or install the bulb correctly. This results in the bulb shorting between multiple circuits. With this being said, if in doubt, remove the bulb and reinstall it, making sure you get the terminals like they need to be. This may involve having to put a mark on the bulb to indicate a specific point on the bulb (ie, black mark in line with the 2 posts in the center of the bulb so you know the terminals are lined up with the contacts). Keep in mind that you can remove the back plate off of the taillight and it will lay on the floor of the trunk. This makes spotting bulbs acting erroneously much easier. For example, hitting only the brakes, you should have a single bulb light up. You see more than 1 light up, see the beginning of this paragraph. That or the tech destroyed the ground wire for the taillight (wouldn't be the first one I have seen).

If you are still having issues, then let me know and we can take what you are seeing and we can go from there. Worst case, I live about 2 hours south of you in California, MD. If you don't mind a drive, I am sure I can figure out the problem in no time flat.

 

Thermo, thank you for the extensive reply. My X-Type standard sedan was built in April 2004. The plug going into the taillights have six wires as follows: green-black-orange-orange-green-orange. There appears to be no damage to these wires.

All of my taillights are working. The brake lights light up only when the brake is applied. In case the mechanic installed the wrong type of bulb, I replaced both dual filament bulbs. The high mount stop light still does not light. My next course of action is to see if the wire to the HMSL came loose.

 

Raven. Ok, unfortunately, you have one of the unicorns when it comes to X-Types. Yes, you have a later generation X-Type with the upgrades, but your wiring harness is from the earlier car. So, when you go to look for a wiring diagram (let me know if you need one), you need the one from 2002 and 2003, not the 2004+ one. This is where this group is helpful as we know these little oddities. Also, the green wires you talk about, look at them a little closer, you are going ot see a thin colored line (in this case a white and a black. So, one wire will be green with a white stripe (your rear fog light) and the other will be green with a black stripe (your reverse light).

With this being said, this changes how the 3rd brake light works. In this case, all 3 of your stop light wires are jointed inside the fuse box under the dash. So, for your 3rd brake light not to work, you have either a bad termination in the fuse box in the dash, a broken wire between the fuse box and the 3rd brake light, or the 3rd brake light has a problem.

To narrow things down. you will need to access the 3rd brake light. You should see 2 wires there, a black wire (ground) and a orange wire with a green stripe (power). If you use a multimeter and do a resistance check of the black wire to the body of the car, you should get a very low resistance (under 5 ohms is acceptable). If you do not get this, the mechanic that messed with your tail light damaged this wire most likely. The ground wire will need to be repaired. Assuming the ground wire is good, next measuring for 12 VDC, apply the brakes and see if you have 12 VDC on the orange/green wire. If yes, then your 3rd brake light housing is bad and it will need to be replaced as I recall it is filled with LEDs and there is no real fixing this. If you do not have 12 VDC there, then I would recommend getting a tool called a "toner". In short, it puts a signal on the wire that with the "antenna probe", you can follow the wire. You would unplug the 3rd brake light and attach the toner to the orange wire through the plug. From there, you can use the antenna and follow the wire through the car (may need to remove a few things like the back seat, possibly the sill plates) to follow the wire. When you loose the signal, this is telling you where the break in the wire is. If you can follow the wire all the way back to the fuse box, then this is telling me that either something before here has been mis-read or the problem is internal to the fuse box

If you do not know what I mean by a toner, the below link is what I am talking about:
I am sure you are going to have questions about how to use the tool. It is not hard and it can be a real time saver.

If you find you have a broken wire, then talk with me. I will tell you how to fix the wire. This is what I do for a living (I do the electronics for a nuclear reactor and have ot make things to survive a meltdown, overkill for what you need, but you can be guaranteed to not have a problem in the future). Kinda like if you think you are getting in over your head, let me know. I will have you come down and I will have what we need to fix this.

 

every forum needs a thermo!
merry and happy christmas to you all

 

Thermo, thank you for the additional information. I looked at the taillight wiring harness and can verify that one green wire has a white stripe and the other green wire has a black stripe.

I removed the 3rd brake light (HMSL) and tested it using a 9-volt battery with the help of my neighbor. The 3rd brake light works. We then used a multimeter to test the ground wire. We did not get any resistance, but this might be user error. We tested the orange/green wire and had no VDC. Once again, this could have been some user error.

I am officially in over my head. I have neither the tools nor the expertise to fix an electrical issue. I am willing to drive to your place if you are still willing to help this senior citizen.

 

Raven, your 9 volt test tells me that the 3rd brake light is functional. So, that is a good thing and eliminates 1 of the potential problems. So, we either have a power issue or a ground issue (looking more like a power issue). But, we can confirm this with a bit more information/confirmation.

For the ground check, we are not going to press any pedals. The checks will be done as the car sits. The first thing is to set up the multimeter. If you look, the multimeter should say "ACV" on one section, "DCV" on another and then either "I" or "A" on another. Then there is a final section that is normally scaled "2M", "200K", "20K", and "2K" (there may be some other scales in there, but this is fairly standard. I want you to turn the dial to the "2K" position. Now, put the red wire to the black wire coming from the 3rd brake light (as close to the brake light as you can, ideally getting on the light side of the connector). You are then going to touch the black lead to any piece of bare metal you can find near the 3rd brake light. You can even use the fasteners that hold the 3rd brake light in place. You should see something less than "5.0" indicating on your multimeter. If you see "OL", then this tells me there is a problem with the ground wire. If you get something inbetween, then write down the value and send it to me and I will tell you what that is telling me.

Now, we are going to shift the multimeter to read "20V" on the "DCV" section of the multimeter. You are going to put the red lead on the orange wire with the green stripe (as close as you can get to the 3rd brake light) and the black lead to any bare piece of metal you can touch. WIth the leads on the points, have a second person touch the brake pedal to turn on the brake lights. If the multimeter jumps up to something around "12.0", then we know the power is getting back to the 3rd brake light. If you are seeing "0.0". This is telling me we have an open wire on the orange/green wire. This will need to get fixed.

There is a potential you have gotten all this way and gotten all good readings. This is actually a good thing. This is where you need to look at where you measured things and everything between the probes you know is good and the portion that is between the 2 probes when you did the 9V battery check is good. You should have a small section of wiring left (maybe 2 pieces). That is where your problem is located.

HOpefully being a bit more descriptive in the checks helps you confirm what you did earlier. I am more than willing to help you out. But, with that being said, I am reaching a busy point in the year for me due to work. So, if we are going to fix this, then we need to do it sooner than later. I do not know how your Sundays look, but that is normally the best day for me for car projects. Let me know.

 

Thermo, my neighbor with the multimeter is extremely busy. Therefore, I purchased a Klein Tools multimeter. It had all of the settings referenced below in your last thread. Thank you for the great test instructions.

After multiple attempts on different days using various metal surfaces for a ground, I received only an "OL" reading for the ground wire check and "0.0" for the orange wire check. There is a good chance of a user error here.

Being that this is your busy season (and wintertime), I can take the Jag to a local repair shop staffed with some good mechanics working on exotic cars. I will provide them with the information you have provided which should allow them to fix the electrical issue.

 

Raven, if you are getting the "OL" for the black wire, then there is your problem. Your ground wire to the 3rd brake light is messed up or not connected. For the orange wire, you have to press the brake pedal as you take the voltage measurement to get the 12 VDC. But, I would try temporarily adding a ground wire from the black lead to a metal spot on the body and then see if the 3rd brake light works. If so, leave the temp wire in and call it good until April when you can come down and I will fix it properly.

 

well done, getting closer!, don't give up yet! 👍

 

Thermo, I gave the information provided below by you to the mechanics at Rebuli Auto Service. The technician verified that there was "no power or ground at the center brake lamp connector. Ground comes from the E post. Power comes from brake pedal switch and splits to all three lamps at unknown location. Left and right brake lamps are working. Need to remove headliner to trace or repair wiring. Fabric is coming off headliner and likely will come off pillars if removed". Neither Rebuli nor I wanted to remove the headliner. Therefore, the mechanic ran a power wire from the driver side taillight and attached the ground wire near the high mount stop light. The HMSL is now working.

The mechanic is not familiar with an E post connection. Where is the E post on a Jaguar?

 

Raven, looking in my manuals, the "E" post is also called "ground post G38AS". Its physical location is at the edge of the headliner in the rear on the driver's side. Where the headliner and the covering for the C pillar meet (on the driver's side) is where that ground post is. But, putting a ground wire to any metal surface near the 3rd brake light works too.

On a side note, if you want an electrical diagram for your car, let me know. I can send you a digital copy. That will be helpful for you in the future. I would also recommend going to the top of the X-Type page and downloading the JTIS. That will give you step by step instructions on how to fix your car. This has a wealth of information in it. PM me your e-mail address and I will get the diagram to you.