The XJ40/81 range is a rather complicated car when it comes to electrical issues, and it is totally different from the XJS range. It is critical to use the correct wiring diagram. Find the correct electrical manual attached.

Instrument lighting and power is managed through switched ground by the ignition lock switch (page 20). You will need to check if you have proper switched ground there.
I would strongly suggest to use this as a starting point and then get to the starting issue later.

I agree with the focus on the ignition switch as a starting point

The ignition switch needs to provide a ground path / enable and is wired the same as earlier

Notice your Linear gear position switches ( near the gear shift box top side ) has to have a ground stud path and possibly the connector / splice in your battery pic post # 24 ( but that looks to be the positive post terminal cable )

This path can be seen on page 22 of the V12 X40 wiring guide as the 20 inverted triangle point

But this path is buried in the center console to verify ground path so that brings you back to verifying the ignition switch which is easier to check

Error

Hey, sorry guys I have a lotta questions and I hope you guys can help me. I have a 1994 jaguar XJ 40 with a V 12 I’m dead in the water right now we’re gonna a while ago, but could not get anything different to happen I have no power to nothing, but when hook the battery up the security thing in the middle Consol lights up but none of dash lights my headlights light up. Can someone please help me I don’t want to give up on it What size of battery in cranking power should I need? Just checking

You already got a lot of help in this thread https://www.jaguarforums.com/forum/x...-263423/page4/ All the details are there. You will need to provide some results from tests so members can continue to help you.

Hi Jmains123,

I have merged your new thread with your previous thread. Please do not start any more threads on this topic - please keep all your posts in this thread to avoid duplicate effort and confusion on the part of other members.

What steps have you taken so far to troubleshoot the symptoms?

Cheers,

Don

I have power to the interior lights and the dash lights come on for the gauges are nothing else work that’s how far I’ve gotten

Please check fuses A3 and A5, left fuse panel. Replace if blown. Only if both are okay, next check the ignition power relay. It does provide power to a number of circuits. It's hidden behind the center console panel. In order to get access to it, you need to remove the radio at least. Please see the attached photo - it's the blue relay on a black base.

Please post your results.

thank you I checked it and it does not click when I press it in with my hand what should I do from here?

The ignition on relay is in the big picture pic on the other thread

It is in in the same set as the center , left , and right fuse panel

All 4 items must click on key rotation

Battery connected

Did you check the fuses?
Did you check the correct relay in the center console?

Maybe this is a fuse box issue? Let's not forget the fuse boxes are major problem as these cars age.

Larry

There was no click from the starter relay only clicking I heard was from the key in the ignition

Sorry, I have to try and get another time. The starter relay in the center consul does click.

I don’t know if it matters but when I try to start it the first time, the windshield wipers normally don’t turn on turned on for just a minute and then I try to after and I didn’t work

Referencing the relay map the relay in the center of the dash is the ignition on relay often referred to as ignition positive relay on normal cars

This relay powers the engine ECU ( error )

The starter relay is on the car's far right but not needed to check just yet for the starting sequence

By the ignition on relay clicking it does prove you have the correct ground command for the center , left , and right fuse panels through the ignition switch ( error )

So what do you want me to do now and thank you again

Place you finger on the center , left , and right fuse panels and feel for a click with key rotation ( error )

Wipers on back burner and may be resolved hunting down your power distribution

sorry I just did that it does not click at least I can’t feel it click is there a think I can check for power?

Coming back out of the fuse panel you can watch for a system being powered as the wipers may be one , but there are a couple of wipeer fuses to see their power source ( panel )

Grilling so may not get back with you until Tuesday