Hey guys, first time making a post on these forms. I recently noticed my jaguar xj8 2006 randomly dying and having to go and shimmy the key around to fix it. so i ended up going and replacing the ignition switch (very annoying) but anyways I go to turn the car on and there’s no power at all, and they old ignition switch is just done there is no limping it or anything so the car is just dead no power at all. I tried going thru all the fuse boxes to see if that’s the problem but again i don’t have power to open the glove box to get to it. if someone as any advice at all on what to do it would be greatly appreciated 👍

 

I think we need to start by verifying that the new switch is actually passing power to the appropriate fuses.
If you have a multimeter then you might like to start with these testing steps.

Roll the ignition switch into accessory position (position 1).
You should now have 12 volts appearing at fuses F7, F8, F11, F20 and F34 of the passenger junction fuse box.
If you do not have any voltage on these fuses then check fuse F41 (20 amp) in the passenger junction fuse box as that supplies the ignition switch assembly.

Rolling the ignition switch into position 2, there will be two tests here.
Firstly you should now also have 12 volts appearing at F15 and F29 of the passenger junction fuse box.
The second fuse group to test is F1, F2, F3 and F4 as a sample group of fuses in the passenger junction fuse box also.
If you have voltage at the first group (F15 and 29) but not at the second sample group of fuses, then you may need to check your inertia switch hasn't somehow been tripped out.

Let's see what results you obtain with these initial voltage checks, then we can decide where to go after that.

 

So my jag has to have power to open the glove box to get to the fuse box, so I can’t open the glove box to get to it

 

Odd; The fuse box in passenger compartment is way below glove box. Actually, I can't access that fuse box with glove box open, I would not attempt to even probe fuses with multimeter probes when it is open.

 

+1 to what big Koshka said.
Fuse box is in lower A pillar, not access via glove box.

Here is a bit of reference info for you.
https://fuse-box.info/jaguar/jaguar-...004-2010-fuses

 

Yea so basically i had just finshed that hassle of a job and said i would address this tomorrow, then the car just started getting power again, worked for like 3 weeks and then boom i park it in the drive way and it doesn’t work again, tested everything one thing i noticed is when i open the door to the back all of the lights are on, when i open the front doors nothings on which leads me to a relay but i can’t find a single diagram for the relays anywhere

 

If you haven't yet downloaded the schematic for your car you can do so by visiting JagRepair.com - Jaguar Repair Information Resource and downloading the schematic for the 2006 XJ8.
http://www.jagrepair.com/images/Elec...al%20Guide.pdf

The interior light schematic is figure 9.1 (page 115) of that electrical manual.
In the schematic you will see the rear door ajar switches are an inputting signals to the rear electronics module, whereas the front door ajar switches are different.
The driver's door ajar switch is inputting to the drivers door module, whereas the passenger's door ajar switch is inputting to the front electronics module.

Specifically, you have the three door zones (Driver door, front passenger door and both rear doors) being fed via different supply pathways.

Drivers door: Referencing Fig. 9.1
Utilizes a supply into the drivers door module noted as coming from fuse F42 of the passenger junction fuse box . drawing reference "square 79" referring back to fig 1.3 page 47.
It also appears to utilize a secondary supply from fuse F28 of the passenger junction fuse box, drawing reference "round 76" from Fig. 1.6, page 53.

Passengers door: Referencing Fig. 9.1
Utilizes a supply into the front electronics module noted as also coming from fuse F42 of the passenger junction fuse box . drawing reference "square 80" referring back to fig 1.3 page 47.
It also appears to utilize a secondary supply from fuse F14 of the passenger junction fuse box, drawing reference "round 64" from Fig. 1.6, page 53.

Both rear doors: Referencing Fig. 9.1
Utilizes a supply into the drear electronics module noted as again coming from fuse F42 of the passenger junction fuse box . drawing reference "square 78" referring back to fig 1.3 page 47.
No secondary supply reference for these doors.

As far as relays go, there is the system relays (R1A and R1B) inbuilt in the passenger junction fuse box that provide switched power that feeds a multitude of fuses including F14 and F28 that affect both front doors.
These system relays are not user replaceable relays as they are integrated and soldered into the fuse box assembly. These relays can become problematic and can be replaced but it is a significant disassembly of the fuse box to gain access to remove and replace the relays with a suitable equivalent. These system relays are commanded to turn on by both the front and rear electronics modules, so if they are being switched on but bad contacts within the relays are making intermittent contact, you will get various systems that are simply not waking up.

Conversely, you could be looking at front or rear electronics modules that are not running properly if they have a bad earth to the module which is also a possibility on these cars. Earth studs into the aluminium are fragile and cause a number of phantom problems.
Look up the earthing points in the electrical schematic manual to give you the location and grounding point numbering that you can refer back to in the relevant schematics.