1985 XJ-SC Fog Light Installation

[b.l.hayward]

Hi All - I installed a pair of genuine Jaguar Fog/Spot Lights a while back and left them unconnected because I couldn't find anything on the loom to match the sockets on the lights! I have decided that I will now connect them to be switched totally separate from the loom ie fused 12volt supply of sufficient power handling, relay, switch etc. I don't really want to run a fused wire from the battery through the interior so my question is where is there a 12v supply in the engine bay of sufficient power handling capability on which to add the lights? Live when the ignition is on or at least when the side lamps/headlights are on. I am happy on schematics (and I have the workshop manuals) but that isn't the same as physically locating what you are looking for!
TIA Brian

[Lastmin]

what about the horn relay? its 20amp and will have power when ignition is on?

Only reason i thought of that is my horn relay currently broken and waiting for a new one. I'm no electrician though.

[b.l.hayward]

Hi Lastmin. Thanks for that suggestion....you sometimes just need a different perspective! Of course! That relay is in the passenger footwell and the feed side should always be live with ignition 'on' and have the current carrying capacity. Thanks again for the pointer

[b.l.hayward]

This all got put on the back-burner (nice to have bit not essential!) but I have just re-kindled my interest to sort out once and for all. According to the circuit diagram in the XJS Repair Operation Manual, if front fog lights were installed (they were an option) they were wired into a red/yellow wire in the front loom (which I have found and connected to the lamps). But I notice that my light switch does not look like the line drawing in my owners handbook insofar as the front fog light icon is missing (but there is a fog light fuse in the Aux Fuse Box, under the dash panel, passenger side) . However, no position of the light switch illuminates the front fog lights so I guess I have the 'wrong' switch for front fog lights? To see if the R/Y wire is connected to a fog light relay (to help chase the feed to the relay) I need to locate the relay. Although it is on the wiring schematic no mention is made of the actual location of the relay. Anybody know where it is physically located?
TIA

[poprivet]

I'm fairly sure that on my '88 the front fog relay is near the fusebox under the steering wheel. The whole panel needs to be dropped not just the fuse cover to see it.

Not sure is the earlier cars are the same but I can't see why they would differ. I suspect yours never had the relay fitted from new?

[b.l.hayward]

Thanks Poprivet - Mine is an '85 V12 HE Cabriolet so I would think that, layout-wise, they should both the same (unless the V12 is different!). I couldn't see any relays around the fuses under the passenger dash so will have a look into the fuse location on the drivers side. But why would Jaguar have fitted a fog light fuse on the passenger side if then they didn't fit a relay I wonder - and why no mention in the ROM, even if it is an option (as was cruise control, which is all there). Rhetorical questions!

[PaulGover]

I vaguely recall a light switch that had a "pull" mode that let you turn the fog lights on, but I don't remember which car it was on. Anyway, try pulling the switch, rather than turning, or maybe pull then turn. No guarantees or refunds, especially if you pull the switch out of the dash

I think the pull only worked on the main-beam setting (so as to ensure you couldn't drive with only fog lamps (which actually is stupid, as headlamps in fog produce lots of backscatter)).

[b.l.hayward]

Thanks Paul - there is only one position on the main light switch where the central knob can be pulled out and that works the rear fogs. In this position there is no power on the front fog feed - the red/yellow wire under the front bumper. Still looking!

[cafcpete]

Not sure if it will answer your question, but the PDF download from this page has some helpful info on all things XJ-S with a section on fog lights.
http://www.jag-lovers.org/xj-s/book/Jaguar.html

[poprivet]

Checked mine today, hopefully this will help.

1. Off.
2. Side lights only
3. Headlights + push to add rear fog lamps
4. Headlights and front fog lamps + push to add rear fog lamps
5. Front fog lamps only + push to add rear fog lamps

[b.l.hayward]

Thanks for the input, guys.
- it looks like my main light switch has no provision for front fogs and it is the one shown in the Parts Catalogue for the XJ-SC HE V12:

V12 Light Switch

- Positions are:
1. Off
2. Side
3. Headlights
4 . Push and turn for Rear Fogs
- have consulted Harvey Palm but it all seems predicated on having the 'right' switch installed - and the ex-works wiring is often wrong, apparently!

As I don't want to start playing around with switches and old connections I am back to the original plan of a separate switched feed, trying to make use of anything already installed.

So what have I got so far:
1. Yellow/Red wire at the front bumper to connect to the front fogs as shown on the ROM schematic - tick
2. Locate the position of the fog relay on a V12. If space but no relay then insert a relay and check whether there is power to it, under any circumstances (this is where I am). Any V12 owners out there with front fogs who can locate the related relay? Then find/install a switch for the relay.
3. If no position for the relay (why, then, put the R/Y wire and fuse in?) then install a relay with power feed taken from the Horn Relay (or any convenient feed capable of 20A) with a separate switch.