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Installing a Battery Disconnect Switch in a Gallardo

The 500+ HP engine of a Gallardo is requires a good battery to crank the car.  If one is working on the car with the doors open etc. running the battery down can happen easily. All older Lamborghinis had a convenient battery disconnect switch that was either in the engine area or inside the car. In later models it was a little more sophisticated in that when the battery was disconnected the radio loose its prefix settings.   Unfortunately in the Gallardo there is no such switch.  You have to disconnect the negative battery terminal every time. A real pain and not good for the battery itself as flexing the terminal post can weaken the battery internal structure.  Fortunately there are many after-market battery "kill switches" at most auto stores. I describe here how to install one.
Fig 1 Battery Disconnect Switch
The Gallardo battery is located in the front of the car (Fig 2). There is a flap at the back of the trunk that opens to expose it.  While it is possible to install most switches without removing the trunk box (see below) I find it much easier to do so with the box removed.  Removing the trunk box is quite easy. If you have not already done so remove the partition that splits the trunk in two (This is required by US regulators so a small child cannot lock themselves in the trunk. Lamborghini did not want to install a hood opening pull wire!).  Anyway the trunk is attached to the frame of the car by 4 screws inside the bottom of the box. Then remove the rubber waterproof seal around the top of the box. It is quite tight but peels off when pulled up.  Next lift the box out of the car. It is quite large and heavy for it's size (fig 3).  Figure 5 & 6 shows the before and after installed key disconnect switch. The switch is shown in Figure 1.  They are very common and are found in most US auto stores. Also see Removing rattles in a Gallardo for more information about removing the trunk box.

Be sure to attach the switch to the negative battery terminal.  You will have to loosen the attachment hook the binds the large negative lead wide to the frame at one place to get more of a length on the wire loser to the battery.   The angle of the switch is not great but it has to be like this so the trunk door flap will close.   The only complication in putting in the trunk box is reattaching the rubber waterproof seal. Having tried a number of way with some frustration let me say the best way is to install the rubber seal first on the car, attaching it all the way around the trunk box plastic frame/holder. Press it down real well. Then insert the trunk box. Now the hard part, with a screwdriver tease the rubber lip of the seal over the top edge of the trunk box. Work all the way around (see fig. 7).  This is not as easy as it looks!

Finally when tightening down the switch to close the circuit always remember to make sure it is tight to avoid a bad battery connection.  This is a simple install and well worth the time and effort.

One point I should mention, for a switch like this it is essential that the green knob of switch be screwed down real tight to close the circuit. If it is loose it will shake open disconnecting the battery leading to possible engine stopping, alternators failure etc.  I now have replaced the above switch with a second more robust switch.  It is one of many found in most well equipped auto stores. It is completely self enclosed and has an on/off knob. If you work on your car a lot and want a more reliable switch then you should use a switch like this (see below).

In order to connect a large switch like this you need a place to put it that is easily accessible. I attached it to the plastic "cover" over the battery as shown in figure 7. The one complication we have is:  the ground lead is too short. A second short lead (fig 8) is needed. This is attached to the battery and one pole of the switch. Disconnect the + wire for the battery while you are doing this. Also make sure all connections are tight. Then you need to cut the battery connector on the ground lead (using a hacksaw) and attach a copper nut attachment post (see fig 9, 10). This needs to be well soldered to the copper lead. I use a propane/oxygen burner to heat the copper lead and melt the solder. It is very important that a good connection is made. Make sure the joint is well soldered. Again attach and tighten this lead to the other switch pole (see fig 7). 

Finally one other small improvement. There is a bracket above the switch that gets in the way of the switch (fig 11, 12 & 13). It holds two wire connectors but sticks down in the way of the switch. Remove the bracket and cut off 1 inch from its bottom (its not needed) and reattach. This allows the switch to sit nicely un-disturbed as shown in figure 14.


Fig 2. Location of battery in Gallardo Fig 3. Trunk "box" removed.
Fig 4.  Battery before switch Fig 5.  Battery with disconnect switch.
Fig 6.  Re-installing trunk rubber seal. Fig 7.  Rotary switch installed over battery.


Fig 8.  Connecting ground wire   Fig 9. Ground wire battery connector removed


Fig 10. Both leads attached ready for switch   Fig 11.  Bracket that needs to be trimmed


Fig 12.  Bracket before trimming   Fig 13.  Bracket after trimming


Fig 14.  Finished Switch    

This page was last modified on 03/12/2014

This page was last modified on 09/06/2014