Hello. I'm new in this forum. I'm a cars amateur and I like adding electrical features to them.

My project is quite simple and probabilly this will be a sillines for you. What I want to do is to install a switch on the exterior of the car that closes the circuit of the trunk latch so I can open it from the exterior, but obviously that switch has to be inoperative when the car is locked. I have already checked that this function is not present in the original car's electronics, I mean there is any circuit that becomes dead when the car is locked so I cannot follow that way. Of course I cannot as well use a relay that is only powered when the car is unlocked because that would drain the battery. The solution will be a some kind of switch that can be opened or closed by reciving the signal from the power locks. But in this field I'm completely lost. I don't know what kind of different electronic components exist other than relays.

I hope you can help me. Thanks.

 

Why not put the switch in parallel to the existing internal trunk latch?

 

Do You have a Car-Alarm-System in the Car ?
They are dirt-cheap, and provide many useful features.
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Why not put the switch in parallel to the existing internal trunk latch?

Because it's on the exterior of the car, so I don't want anybody opening my trunk although the car is locked.
I clarify, when the car is locked the interior trunk switch still works normally.

 

Do You have a Car-Alarm-System in the Car ?
They are dirt-cheap, and provide many useful features.
.
.
.

I haven't thought of that, but seeing that that's one of your solutions makes me think the project is not as easy as I thought. I would prefer not adding modules or weird systems. I thought there could be simple switches or something that could be actuated by the locking/unlocking signal.

 

It's almost certainly more complex than You thought.

You must have either a source of 12-Volts when the Car is unlocked, or,
an available switched-Ground when the Car is unlocked.
These 2 Voltage-Sources must reverse their state depending upon
the Car being locked or unlocked.

After You have one or the other Voltage-Sources available, the rest is easy.

All Basic-Car-Alarms have a "Starter-Inhibit" Output-Wire which would be perfect for this application.
Not only that, most Car Alarms have a Remote-Control "Key-Fob" with a Button that is
specifically for unlocking the Trunk, (or Boot ),
this would completely eliminate the need for drilling a hole in your Car for an external Key-Switch.
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when the car is locked the interior trunk switch still works normally.

Oh Oh..