Mystery black box - any idea what it is?

[Ralfj]

I've just taken ownership of a 1992 4.0 XJS and I'm in love. She has a number if issues that need to be sorted, some just cosmetic and some more functional. So I'm starting to compile a list of things I need to tackle. One of these is an intermittent problem with the central locking, which seems to work randomly. However, I'm wondering if it might be something related to operation of the bonnet release lever. Whilst exploring the area looking for possible shorts, I noticed a mysterious little black box with two LEDs and I'm unsure if it's a factory item or not and what it might do.

https://photos.app.goo.gl/FRWB1vxiZm8XcFLH8

In case it's some kind of immobiliser, before I start poking around I thought I would ask if anyone here had an idea what it might be?

Thanks

Ralf

[davidr]

Hi Ralf - I'd like to help but I'm having trouble accessing the photo. Please could you place it directly in your post instead of a link to a hosting site?

[Tris]

It looks like the cover for the inertia sensor.

[ptjs1]

Agreed,

It's just a plastic £2.50 cover for the inertia switch. The two nobbles are just part of the cover not LEDs.

The central locking issue won't be impacted by the bonnet release lever which is just mechanical.

Good luck with your investigations.

Paul

[Ralfj]

Thanks everyone. Mystery cleared up and I know to leave it alone and not worry about it.

In terms of the central locking, there is definitely a correlation between the bonnet being opened and closed and the central locking stopping working, which makes me think it might be a short or some other connection issue in that area as I assume the wires from the passenger door come through that general area. However having read a few things on here and elsewhere, I'm going to take the door cards off, give the mechanisms a good lubricate and confirm that the microswitches are functioning properly. Worse case I make sure the locks are not going to stick or jam on me, best case I fix the problem.

Cheers

Ralf

[poprivet]

The wiring above the inertia sensor looks like Mr Diy has been in there. Maybe an aftermarket alarm or immobiliser?

Check the bonnet catch, it can rub on a wiring loom when the bonnet is closed which could cause a short, you should be able to see if any wiring insulation is worn away.

Al

[PaulGover]

... I'm going to take the door cards off, give the mechanisms a good lubricate...

Use grease, not WD40 or oil. I made the mistake of WD40, which stopped the locks sticking - for a few months. After that, it all seized again. AFAIR the manual does say grease somewhere.

[Ralfj]

Thanks for the tip Paul.

I took the door cards off yesterday and apart from finding out why the front speakers don't work (because the cones have literally disintegrated ) I couldn't see anything wrong mechanically with the locks, all seem to move freely. I still can't help think its electrical as it stops working intermittently and when it has stopped then neither door will trigger it and the boot doesn't unlock. I noticed that the driver's door has a connector on the wiring loom from the solenoid, so I'm going to check the pins in there and make sure they are properly mated.

I don't suppose you know where I could find a wiring diagram for the locking system? I brought the manuals from eManual but TBH haven't found them very useful? Without the wiring diagram I am worried I'll end up being sucked into a vortex trying to trace the cables through the main loom

Cheers

[PaulGover]

The manuals should come with a set of wiring diagrams (section 86.x.x as far as I remember), though of course you're at the mercy of whoever compiled your manuals from eManual.

You probably don't want to know, but the official Jaguar manuals on DVD/USB key are available for £75 from SNG Barratt among others:
https://www.sngbarratt.com/uk/#!/Englis ... /44/1/10/1
or as an on-line e-book. I'd phone them to check up exactly what's on each. The full set of workshop manuals was in 5 volumes; Jaguar offered them all on one of their DVDs which I'd hope is what you get on the USB stick. There's also a single volume manual which, while usable, is obviously less detailed than the full set. That appears to be the "Workshop manual" printed version on Barratt's web site. (The 5 volume set has alternative sections for items that changed with later model years.

[ptjs1]

Ralf,

Have a look at the attached and you'll find what you need in Fig 12.

http://www.jagrepair.com/images/Electri ... trical.pdf

Bear in mind that the diags are for a LHD 92MY, but basically, it's the same as yours.

Hope that helps.

Good luck

Paul

[Ralfj]

Thank you so much Paul, this is perfect. I've just cheekily printed it out at work and look forward to some bedtime reading

[ptjs1]

A pleasure.

Let us all know how you get on.

Cheers

Paul

[Ralfj]

Quick update on the central locking issue. By pure random chance, I was in the car earlier today and someone came to talk to me, so I put down the passenger window, and all of a sudden the passenger door and boot unlocked. From that point on the locking worked perfectly.

I've not had any time to investigate further yet, but it looks like it could be a short or bad connection somewhere around the passenger door solenoid assembly. Which would kind of tie into my correlation with opening the bonnet as that requires the passenger door to be opened and closed. At least I know what I'm doing on Saturday morning now.