I can't seem to get the rear fogs to work, headlights on low, front fogs on, but no rears. Had a look at the tailight unit but could not even find the bulb, just the reverse and signal bulbs,(I think). 2004 XJR. Any suggestions? Thanks.

Stu

 

The rear Fogs are the "Brown" bulb holder/connectors (#3).

Rear fuse box:
Fog and reverse lights, left and right sides: F-17 & F-46

Did you press the rear fog light switch?

 

Thanks Reyes, so the reverse and fogs are on the same fuse, my reverse lights work so it must be the bulbs. Didn't see the the brown bulb holder, will have another look. Yes I pushed the rear fog button on, also did not get the rear fog indicator on in the dash, so could also be a switch problem.

Stu

 

Any success on your rear fogs?

 

Not yet, too cold outside, -20C, I keep the car in an unheated garage. First thing I'll do is check the bulbs when it warms up.

Stu

 

Totally understandable.

It is currently 23.3 F here and my unheated garage is 58 F, must be the insulation that is keeping it at that temp. I was planning on replacing the J-gate this weekend but I think I will put that off another week.

 

Wow! 80F today in south Florida.

 

Warmed up to +8C today so checked the bulbs and they are ok. Must be the switch. Does anyone know how to remove the switch assembly, does it pop out or do I have to remove the little cubby holder below it ? Thx

Stu

 

Tried another switch and no luck. Does anyone know if there is a relay for the rears? Is this something that could be activated/ deactivated by the WDS for different markets? I'm not getting the amber indicator in the instruement cluster either, although I get the front. Thx

Stu

 

Ever sorted this out?

 

I am having the same problems. indicators and reverse lights on the same fuse all ok. the front fogs ok as is the green dashlight light, the rear fogs neither the amber dashbaord light or the rear fog lights come on. According to the manual the switch is a resistor array. the resistances measured dont appear to be the same as the book, however I tried a series of resistors as per the book and can still only get the front fogs to work. took one of the fog lamps out and tested it and it works fine.

 

Hi Jaguar NZL,

What year is your X350 as there can be some electronic module and schematic changes throughout the production time frame?

Rear fog lamp switch for RHD models is grounding that lighting input to instrument cluster with a 820 ohm resistor.
Front fog light switch grounds same line but with 470 ohm resistor.
This is reversed for LHD models.

If it is not an input problem form the fog control switches, then it is likely either an output problem form the rear electronics module or a bad earth as there are several earth wires from the rear electronics module to grounding point G24 which is just behind the right rear wheel arch.

 

Just a further note to be made on the functionality of the fog light switches....

The front fogs can be activated when you have the park, main or high beam lights set on the lighting stalk switch.
When I checked mine this morning, I found the rear fog lights were only selectable when the lighting stalk was set to either main and high beam.
Rear fogs are not available when you are just on park lights setting, but the front fogs are.

Just wanted to clarify that for you so you don't try to hunt a phantom fault if you happen to just be on park lights.

 

Just to back up H20toSteam,
Here is the relevant page from the owner's manual



Pete M

 

Thanks Pete,
I was only testing the switches individually and forgot to check if the rears would in fact come on with the fronts already on and only park lights lit.
Makes sense they put that override in the rear module programming.
I thought is was a bit daft the rears wouldn't switch in on park lights....obviously they can .....but front fogs have to be on first.

My Santa Fe could switch the rear fogs on and off at will....great way to back of the tweeny tailgaters!

 

Cheers Team, I think I have tried all those things above. To summarise though. there is power going to the rear fog lamps the power control switch the negatives or return not the positives (tick). The grounds from the connectors Cr 71 73 and 11 seem to be ok(tick) but I wil lcheck them again. Ignition in position 2 (dashboard warning lights on for example head lights on low beam) front fogs light up as does the dashboard light for it(tick), but the rear fog dashboard light does not come on and neither do the rear fog lights. At this stage i would like to know if the dashboard light for the rear fogs is a driven as feedback from the rear module or does it rely soley on the user entry to the dashboard switch (and any other permissives such as ignition being on and head lights on low beam and front fogs on). This might give me a clue as to whether I should be chasing a problem at the front of the car or the rear of the car. i have tried a resistor ladder network like the one in the drawings and couldn't get any progress on the fog light dash switch operation.

 

Not chased this problem before, so I can only hypothesise.

I still suspect you have a input issue with the instrument cluster not detecting the correct grounding resistance being applied to IP7 pin 6.
Your testing with a "resistor ladder" - did you prove you can emulate the fog switch assembly operation by putting a 470 ohm in parallel to the 3900 ohm which should give you front fog light activation. (Between pins 6 and 7 of fog light switch assembly connector IP33 for RHD cars with the switch assembly disconnected).
Then by putting an 820 ohm resistor in parallel to just the 3900 ohm resistor should emulate the rear fog switch being pressed?
Did you happen to check the integrity of the fog switch earth, as if it were somewhat resistive, then that could create a misreading of the switched resistances (just falling outside the sensing threshold of the instrument cluster input).

I would imagine as the fog light switches are feeding into the instrument cluster that is then sending the command via serial data comms to rear module, that the instrument fog indication light should respond to the switch input regardless of the rear fogs actually turning on via a output from the rear module.

If you find you have a cluster issue or rear module issue and just want to have rear fogs activate when you turn on the front fogs, then you probably just want to pick up a 12 volt feed from Fuse 18 which is the front fog switching relay, taking that into a separate aftermarket accessory relay coil which then you use to ground the rear fogs wire that you will disconnect from the rear electronics module CR77 pin 10. That will give you rear fog activation whenever you activate front fogs.
However I would not be sure if a testing station will allow you to run that mod.

If not then we could possibly come up with a small comparator circuit to detect the rear fog switch resistance to then trigger a grounding relay, so the rear fogs could only come on if fronts are active but at least the rear switch would still be somewhat independently operable.

 

My feeling is you are right about the cluster. I made a new ladder network today with the 3.9KR and the 820 and 470 ohm resistors. When the buttons are pushed this gives me 680 ohms and 420 ohms (resistors in parallel blah blah) compare this to the Jaguar switch module with no switches pressed at 1084 ohms (which seems way wrong it should be 3.9K) and front fog switch closed give 592 ohms and rear fog sw closed gives 256 ohms. The encumbant Jaguar switch turns on the front fogs appropriately and no response at all to the rear fog sw. Put in my test box now and the 820 ohms turns on my front fogs (this is incorrect as I have a RHD car the front fogs should respond to the 470 ohm resistor) and the other switch at 470ohm no response what so ever. So I suspect its either a fault in the cluster or a programming issue (or both). I can't for the life of me think why they would have opposite resistors or LHD and RHD other than it was some sort of stuff up making the switch cluster. I did ring Jaguar in Hamilton (NZL) but they weren't particularly helpful. The switch circuit BTW gives about 11 volts with no load and one side appears to be grounded (continuity to ground). I might ring the Auckland fellas and see if they will talk to me. Are there some countries where fog lights are illegal?

 

I'm unsure about fog lights being illegal in any country, but for example for you and I living in NZ, running fog lights when there isn't fog is technically illegal due to their upward lighting angle being difficult for oncoming drivers. (not that there is enough enforcement manpower for such things). But the car systems don't identify if fog is present, so that can't be written into the control module operating parameters.

The resistance readings of your switch assembly seem very odd compared to the published schematic.
What year is your x350? There were some production changes during the years this model was produced but the control switch array appears to be the same throughout?
Was the Yellow/Blue stripe wire going into IP33 pin 5 or pin 6? I expect Pin 6 for RHD wiring looms.

Sounds like you have some pretty handy electronics knowledge in your background.

If I get a chance over the weekend I hopefully can pop out my switch assembly and do some comparison resistance measurements for you.
That will at least confirm what the resting state resistance of mine is and what resistance is delivered when each switch is pressed.

If the answer is not straight forward, then I think you might be ultimately tempted in doing a retro fit of a secondary relay that bypasses the instrument cluster and rear electronics module.
You won't get the instrument cluster rear fog light displayed, but you could still achieve functional lights.

 

This brings up a very good point, just because others are doing it, that doesn't make it legal! Suggest all owners in the USA to check with their State Vehicle Codes on that. The use of fog lights are actually illegal in many States. Here in Missouri for example, fog lights are only to be used during low visibility but, 30% of younger drivers use it all the time.