Just this evening I got pulled over because none of my taillights or front parking lamps were working. The funny thing is I checked this just a week or so ago and everything was fine then.
This is a 1994 XJ6 with the battery in the trunk. The headlights work fine as well as the brake lights and reverse lamps. Also the hazard lamps work.
So if I turn on the four way flashers, the various front and rear running lamps do indeed flash.
Other info, the power seat controls and the cigar lighter still function.
I looked for a fuse that would control all of these but I did not see a master fuse for the running lights.
I did some research and found a mention of the DBC10009 light control relay so I was able to unplug that and then replug it a couple of times just now but no change in the car's condition.
Still no working running lights.

 

On the 1992, I had no exterior lights. None.
I replaced all of the bulbs including the expensive headlamp bulbs 2 9005 @ $22.95 and 2 9006 @$24.95.
Still 'no lights'
Today, I replaced the 4 BFMs with ones I picked up from the junkyard and now all my lights work except for my left and right signals, Hazard lights and door lights.
I had also picked the signal/horn switch and the hazard light switch from the JY, so I will see if replacing them solve the problem.
@JensenHealey: Did you get the PM I sent you?

 

Hi Steve,

Over the years we owned a '93 I had constant problems with tail lamp bulb sockets corroding or the central terminal or "hot contact" weakening and not making good contact with the tip of the bulb or "foot contact". This was usually rectified by removing the bulb, cleaning the socket and hot contact with a fiberglass nick-sanding pen and pulling the hot contact upward a bit with needle nose pliers to improve the spring force against the bulb foot contact. But we never had all of the tail lamps out at the same time.

With the schematic you should be able to work your way from the tail lamps upstream until you find the point of failure. You can download the guide here:

Jaguar XJ40 Electrical Guide 1993-1994

Cheers,

Don

 

I have temporarily solved the problem by taking the DBC10009 relay out of the car, disassembling it from it's case and "playing" with the relay contacts. The relay was remarkably clean inside with no corrosion or anything on the circuit board. I did this a couple of times and then re-installed the relay. It then worked upon installation and has mostly worked reliably since. However one time, this evening in fact, I got in the car and did not think the running lights turned on. I reached over under the passenger's dash and tapped on the DBC10009 relay case and then the lights snapped on. So it is not 100% reliable but probably 76% - 85% reliable. So as a result I have been checking the state of the running lights before pulling away when I have to drive that car at night.

I have ordered a spare relay from a seller on ebay so I will have one just in case.

 

A very common problem is cold/starved/cracked solder joints on the circuit boards, especially around the relay pins. Re-flowing and supplementing the solder usually restores 100% performance.

Cheers,

Don