The Mysterious Fuse - F40

C

carboyben

New member
Hi everyone,

I've been trying to track down an annoying battery drain (about 350mA) on my F Type R AWD Coupe, and hooked up a multimeter in series with the battery so I could start pulling fuses.

When I got to the passenger footwell fuse box, there was a 5A fuse in slot F40 which isn't labelled in the owners manual. It appears that this should be empty.

When I pulled it out something clicked and the current draw from the car dropped, so it could be the culprit. Everything looked like it was working with this fuse pulled, apart from... I couldn't start the car. The ignition would turn on with the first press of the start button (instruments on etc), but on the second button press nothing happened, and then after a few seconds it went back into ignition off.

Popped the fuse back in, car starts as normal!

Does anyone know what this mysterious unlabelled fuse is? Am I the only person with a fuse in that position?
 
Are you 100% sure it's f40?

https://www.youtube.com/watch?v=bLeX0bJdYso

https://www.youtube.com/watch?v=vBiJKef2_HE
 
Yup, 100% certain.

I've found it in the wiring diagrams too, it's very suspiciously labelled:

f40.jpg

Connectors that aren't in use are marked "NOT USED" as you can see from the one below.

This one isn't "NOT USED" but the wiring diagram only shows that it goes to a connector and no further than that.

Makes me suspect it's something to do with the immobiliser or the anti-theft systems. If I had topix I could look up where that connector actually is, but alas I don't. I think because it is shown on here as being used for something, it's probably not an aftermarket device that's been fitted to my car.
 
If the car won't start with it out, and the battery drains when it's in, sounds like something to take out whenever the car is not in use :)
 
Not sure if it helps you much as JLR may well utilise different fuse number over time, but according to Topix for my specific car Fuse F40 is:

Located in: Passenger side foot-well fuse box:
5A Tan coloured
Circuit: Driver door window switch, Instrument pack control

There is no other manual reference to it, nor the C3BP01CR-6 you highlight
 
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