My '85 XJS had a cracked/broken tail light lens.
I replaced the lens and the bulbs, but now the tail light doesn't light up when I turn the lights on. The turn signal and brake lights work just fine. It's just the tail light.

I've:

Replaced the bulbs
Checked the fuses (see below)
Wire brushed the contacts as best I could.

The fuses confuse me. I can't tell which ones go to which. I think they're fine because (as I said) the other lights work.

Any suggestions?

 

As I recall the left tail light is on the same fuse as the right license light, and vice versa. If your license lamps work (do they?) it isn't a fuse.

The fuse for the right tail light/left license lamp is behind the right tail light, sorta tucked up in the wiring...and in the symetrical location for the left side.

Double check the sockets. I just worked on an '89 where I had to clean and lube the sockets a couple times before the tail lights would work reliably.

Cheers
DD

 

The licence light works (the one where there's a bulb in it anyway... I think that's the right one that's working... Hmm, it's not a series circuit, is it? )

What do you use to clean/lube the sockets?


EDIT:
I just double checked; the left license plate light socket doesn't work (I switched the light from the right side which is working). It appears that the fuse is good in the right side fuse holder thing. Also, the front right side runner light isn't lighting; is that symptomatic of this issue as well?

 

Nope, parallel




A brush with WD40 or PB Blaster or whatever aerosol solvent is closest. The idea is to make sure that the spring-loaded base of the socket works freely. If not, there won't be enough spring tension for the contact to firmly hit the bulb. I use aerosol lithium to lube the bulbs and sockets but just about anything will work: vaseline, silicone paste, whatever



Ok, well, which side tail light isn't working? You never mentioned :-)



[quote Also, the front right side runner light isn't lighting; is that symptomatic of this issue as well?[/QUOTE]


The front lamps are on their own fuses.

By the way, "appears good" isn't good enough when checking fuses ! Replace with a known good fuse and/or check the fuse with a meter. Sometimes the wire is broken under the metal cap where you can't see...especially on elderly Lucas fuses. Also, the fuse contacts can be dirty/corroded.

About 95% of inoperative lights on these old Jags is caused by dirty/loose/corroded contacts and/or broken/dirty/loose/corroded fuses. Hang in there...you'll have 'em working in no time !

Cheers
DD

 

Okay, here's the rundown:

The front right parking light (the one in the bumper) is inop.*
The front right side marker light is inop.
The right tail light is inop.
The left licence plate light is inop.

The left side is working as one would expect: the turn signal flashes, the brake light comes on when the brake pedal's depressed, the tail light comes on when I turn the lights on.

Both reverse indicator lights come on.

*The front right parking light in the bumper works when the turn signal is on, it signals like it's supposed to
The right rear brake light comes on when the brake pedal's depressed.
The right rear turn signal works as one would expect.
The right licence plate light works.

I think that's everything that's weird/confusing.

I ran out of light (haha), but tomorrow I'll give the fuses another going over. Is there something I need to pick up to clean the fuse contacts? Or will the WD-40 work for that as well?

And if I haven't said it yet: thanks for the help. I love this car, but it's definitely going to take some getting used to!

 

It's not so confusing when you remember that the signals, brake lamps, and running lamps are on different circuits. So, for instance, the fact the the brake lamps do work while the tail lamps don't is perfectly logical.

The bulbs in the front bumper have two elements---high for signals and low for running/park lamps---on different circuits.

A dremel tool is great for cleaning bulb sockets and fuse holders. Lacking that, a stiff brush or sandpaper...if you can get in there with it. The WD40 (or whatever) just helps soften whatever dirt or corrosion you are trying to remove.




Well this suggests a fuse problem....assuming the license lamp isn't inoperative for a reason of its own :-)

Here's a tip: whenever you are working on the car take a few minutes to clean any contacts, connectors, grounds, etc that happen to be in the area you are working on. Or take a Saturday and clean 'em all at once, every one you can find. It'll go a long way towards happiness down the road :-)

Cheers
DD

 

Okay, I replaced all the fuses. I cleaned the contacts as I replaced them.
Still nothing on the right tail light or the right marker or the left side licence plate.

I found the fuse boxes on the underside of the dash (left and right) and one along the left side of the car under the bonnet (what are these for?).

If I'm missing some fuses, let me know; I want this to work, so any suggestions would be appreciated.

Along the right side in the boot there's a couple of relays that look in pretty bad shape. What're these for?

Also (and I hope I'm not violating some forum law here), but I have some pics of something in the engine that looks broken, but I have no idea what it is.

http://farm4.static.flickr.com/3410/...2fdf4cb28d.jpg

http://farm4.static.flickr.com/3318/...93b863f1ab.jpg

http://farm4.static.flickr.com/3345/...7f193ca5cd.jpg

I'd appreciate an ID on this so I can look for a replacement part/procedure.

Thanks for the help!

 

The broken part is the cruise control bellows.

Do you have a 12volt test light or a volt meter? We're gonna need to do some testing to see where the voltage stops. I suspect a faulty bulb failure unit at this point.

The undrehood fuse box is for the cooling fan and the headlights.

The relays are probably the "main" fuel injection relay and the fuel pump relay. Give me the wire colors and I can tell you.

Not sure about the missing fuses. Possibly for equipment that the car wasn't built with. Or...do you have anything else that isn't working? Isn't there a label on the dashboard panels that cover the fuses?

Post back
DD

 

Cruise control bellows. Great, thanks!
I have a volt/multi-meter, but the battery is dead, and I didn't have another one just sitting around. I'll pick one up. A 'faulty bulb failure unit'... ?

I wasn't asking about missing fuses, actually; I was asking if I had missed any fuse box locations. I don't think I have; I've scoured the car fairly well.

There's a label on the dashboard panel covers for those fuses, not the one in the engine compartment.

There is some stuff that isn't working still (A/C, Cruise)... but I knew those weren't working.

 

Heh heh. Jaguar had a dastardly habit of hiding fuses all over the car...one of the design quirks I can't forgive. I can't remember where they all are.

The bulb failure units are basically heat activated switches that turn on the instrument panel wanring light if a bulb fails.

When you get your battery give a shout and I'll tell you how to check 'em out.

Cheers
DD

 

Go ahead and give me the HOW-TO on that. I'll pick up a battery for the multimeter today and get that taken care of tonight (unless I need a part?)

Also, is the door handle on the 89s the same as on the 85s? My driver door handle doesn't work: the bar that links the handle bit to the door release cables is broken and crawling across the car is starting to get a little old. I know a guy that has a car that he's parting out, but I wanted to double check.

 

The bulb failure unit should be near the fuel pump and main relays in the trunk, right side. The left side BFU is in the symetric location on the left. You are looking for a retangular metallic can with 3 terminals, about 1.25" long.. The wires will be red/orange, red, and white/slate for the right side BFU and red/slate, red, and white/slate for the left side BFU.

With the lights turned on you should have 12v to the red/orange (or red/slate) wires as these are the voltage input wires. If no voltage at these wires you'll have to start looking upstream towards the headlight switch.

The red wires are voltage output to the fuses and tail lights themselves. They should have voltage, too, if the ligts are on. If no voltage here you got a bad BFU (assuming, of course, you had input voltage as mentioned above)

The white/slate wires go to the warning light in the dash.

Hope this helps

DD

 

I got it working; I cleaned the BFM contacts and double checked the order and I think one was on the wrong contact. The tail light is now working. I'm down to the marker light on the right side now, and then I'll be good to go with the externals. Thanks for all the help.