DIY cheap&easy electronic BootLid opener for Lotus elise (last edit: 18.03.2011)

The Number of people who suffered from a failure of the Boot Lid opener cable seems not small to me. The hassle of opening the locked lid in such a case has been reported being a RPIA (a Royal Pain in the Ass)
So, while converting my RHD Lotus Elise to a LHD one, I decided to follow the suggestion of some smart people and install a backup solution to the cable.
Using a standard central lock actuator, a standard automotive relay and a pushbutton, the job can be done for about 15 Euros and in about two hours of time.

So here we start. This is a picture of the actuator and the pull rod, as it should be in your ebay package. Actually, you can obtain a set of 4 actuators including remote control for less than 20 €, but we will only use only one and discard the remote.

And this is, what we want it to look like, when we are done.

The most tricky part might be the construction of the pull rod, if you haven´t such a guy like me around, who already did it before. :-) So here´s my suggestion, how to do it. It works very well, and beside a single small hole you have to drill into the Boot Lid Lock housing, no special modifications are necessary. So here´s how you have to bend the rod.

On the next picture you can see, where I drilled the hole into the Boot Lid Lock housing. It´s about 5mm top and left of the hole where the cable runs into the housing. Please pay attention how the pull rod is oriented and connected to the actuator. Only in this way it is guaranteed that the actuator is under the clam and does not disturb in any way.

After we´ve drilled the hole, we can put the actuator and pull rod in place. The picture below should explain, where the pull rod has to be positioned in the Boot Lid Lock assembly. The rod runs parallel to the cable into the housing, and hooks behind the latch, right in the corner where also the cable is fixed. The picture is not from my car (which was a RHD one) but seems from an LHD Elise. But I think you got the idea.
Because the rod is fixed at the actuator, and any movement is restricted to the one from the actuator, there´s no additional fixing necessary. You only have to mount the actuator fully retracted and with a slight tension against the Boot Lid Lock spring.

Here´s a picture from below. I mounted the actuator with two M3 screws and two 5mm spacers to the existing plastic bracket. The bracket seems strong and stable enough to to the job. If you would like doing it perfect, you might want to consider, replacing the plastic Bracket by a piece of Aluminium.

Last step is to route the wires to your desired pushbutton position. I decided to do it at the position of the LHD Boot Lid cable.

The remaining thing we have to do is connecting a standard automotive relay to the actuator. The actuator draws more than 4 ampere of current, and no standard pushbutton would survive this torture for an extended time. Below you can find the connection diagram. The numbers in the schema represent the numbers as printed on the relay. The pushbutton switches ground (chassis) and activates the relay, which then switches the high current for the actuator.
In my MK-1 Elise there´s a 20A fuse for the fuel pump next to the ECU in the boot. I took 12V from the purple cable and chassis/ground from the cassis bolt