I just got my fogs working! It was all plug-and-play! I have a 1996 but it is the same procedure for 1993.5 to 1996 models (6 cylinder cars- the v12's came with fogs standard).
All you need is the 'short link' seen here:

It plugs into the socket that is found above the row of relays on the left side of the steering column up under the dash, easily seen when the knee bolster panel is taken off (only held on by a stud and rubber clips- just pull down on it!)
Then you just need the proper double fog switch plugged in (swapped for the hazard+rear fog switch), then plug in your fogs to the connectors found in the front bumper facia and done!

 

You also need to replace the hazard switch with the new hazard/rear defroster switch. Number 5 in the picture. number 3 is the dual fog light switch.

 

You can replace it with an original, or send them off to be re-built (rather, have them combined) into the proper switch.
Jerryjag on ebay did it for me, here is one of his listings for the switches. https://www.ebay.com/itm/Jaguar-XJS-...UAAOSwoLpagzk2

I didn't want original Hella/Jaguar fogs so I found some I like better. Anyone can do the same, you just have to either find the correct Jaguar connectors to add onto your chosen lights, or cut off the original connectors on the car and replace them with another type. Either way, you'll get working fogs!

 

I purchased both switch sets from my local Jaguar dealership for a lot less. Not sure if they are still available, but I would try there first.

 

As a follow up, I have recently swapped out my aftermarket yellow lights for a set of originals but damnit if they don't blow the fuse every time after only a few seconds! Could be the wrong bulbs in?

 

When I installed mine on my 94 I had to install a different dash switch pac and it required a bit of fiddling =Rontoo.UOTE
aldP
after the installation I had a bunch of electrical issues with short circcircuits, fuses and lamps blowing.
I had to remove the fog lights after the glass lenses cracked.

;745405]I installed a set of factory front fog lights on my 95 XJS. The lights plugged into the wiring harness, relay was already there. Replaced the panel switches with the correct switches. Lights did not come on, the rear lights work as they should. I have power to the fog light relay, jumped the relay, front fog lights came on and the instrument indicator light was lit. So all is well with the power side and the light grounds. Fog light switch does not light up like the rear fog light switch does. I did swap out the relay with a known working relay... no change. The fog light switch is not picking power to operate the fog light relay. I have tried the switch with the headlights on / off / and high beam, no fog lights yet. The fog light switch assembly is new and I have two of them tried both with the same results. What do I look at next?[/QUOTE]

 

Equiprx, The missing link in your situation is the shorting link plug. You have to purchase it and then it plugs into the socket up inside the left knee bolster under the steering wheel. It provides power to the fog light switch! Look for the terms "short link plug Jaguar fog" on eBay and you should find one.