While troubleshooting my alternator issues, I was checking relays and fuses in the LH and RH engine bay because the RH fuse box has the fuse for the alternator regulator....

Anyway, something I noticed is that three fuses were different values than what the manual indicates they should be.

In the LH engine bay fuse box, fuse F18 for the "fog lamps" is indicated in the manual to be a 10 amp fuse, but a 15 amp fuse is installed and looks very OEM.

Also in both the LH F5 and RH F18 engine bay fuse boxes fuses the fuses for the side/tail/number lights are shown as 10 am fuses in the manual, but installed are 5 amp fuses and again look very OEM.

Is this typical where the actual factory installed fuse values can vary from the vehicle care manual?

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Not typical in any car however the x300 came with a bunch of factory fuse spares under the hood in the tool compartment. If i had to guess someone used the wrong amp fuses when replacing them from the spares.

Good point, and I thought the same, but then again none of my "spares" are missing or seem to not be OEM.

Though it seems less likely if both of the same 5 amp fuses in disparate fuse boxes for the same systems(side/tail/number lights) have been incorrectly changed. Sure someone could have blown the right and left side/tail/number lights at some point and then used 5 amp versus the manual specified 10 amp fuses, but both? Makes me wonder.

Not a big deal, other than I wonder if I should replace these three examples with what the manual specifies, or leave the "incorrect" in place.

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With my limited experience with a Jaguar I faintly recall someone mentioning a upsizing of I believe the sidemarker fuse from 5 to 10 . This may be documented somewhere in the TSB's or others such as this supplemental linked below and the primary wiring guide that may have never been updated .

http://www.jagrepair.com/images/Auto.../jagxj1996.pdf.....page 34

and the below file page 21

I had the same question a few months ago as I was blowing fuse #F18 on the right side multiple times. Both my XJ6s had 5 amp fuses original from the factory to do both side lamps. The printed fuse map inside the lid of the tool-spare fuse box shows both of them as 5amp. I have seen a later list that these are now 10amp.

I had changed out the 5amp multiple times and then substituted a 10 amp fuse which also blew, both would take a couple of days to a week to go bad. I removed the right front fuse box looking for a bad wire, I did put a little electrical tape around where the wire hits the fender but I did not see any worn wires.

What did seem to work was that I disconnected inside the trunk lid, the connector for the outside push button that controls the lock. It has been a couple on months now and no more blown fuses. I actually thought I was disconnecting the license plate light since both of my lights for this are missing and I thought a wire was shorting out. I had read on the Forum that someone else had found this to be the problem.

Once the weather warms up I need to replace the license plate lights and figure out what is going on with the trunk release buttons

Scotland , there are multiple references to the chaffed wire under the boot right hinge plastic cover for the items in the boot lid as they are electrically tapped into things other then the boot lid items .

You can cut the wire to isolate the source of the short as you drive it for a while .

The release button is a different and separate wire from the lamps .