My 2007 S Type jaguar battery is dead and the key wont open the trunk. If I hook a battery charger positive cable to the alternator and a...

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Hi Charles,

Make sure that you are not using the valet key to open the trunk. The valet key will not work there. Here are your other options. 

1. Use a battery charger that charges the car battery thru the cigarette lighter. You might also check the local automotive supply houses to see if they have a cigarette lighter charger. The only requirement is that the cigarette lighter socket must be on in order to backfeed to the battery.

2. Jack up the car and hook a battery charger or a spare battery to the FAT wire on the starter and the neg cable to the chassis. The FAT wire goes directly to the battery. it is fused so dont try to start it that way but you will be able to open the trunk and operate the security system after that. Then disconnect it and jump start your car battery.

Let me know if you have further questions. 

The postive should be to the starter not to the alternator. The negative cable to the chassis or body ground. 

No It wont for as long as you will not start the engine. If the alternator is much more accessible then thats  fine as well. Make sure not to start the engine. Just tap the wires and open thr trunk then unplug the wires immediately. 

Any update on this issue, Charles? 

Dear Charles, It was a pleasure helping you with your Jaguar issue today. Here is a summary of the resolution.
Issue identified :  battery dead , trunk wont open 
Solution Implemented : told cx to connect the postive jumpwire to the alternator and the negative to the body to supply power to the vehicle to open the trunk. cx followed the direction and was able to open the trunk. problem solved. 
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