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Adding this motion sensor to the OEM alarm is pretty easy once you find the correct trigger point, which in the 2007 GTI is the hood switch:
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The switch has two wires, Pin #1 and Pin #2. Pin #1 is always grounded thus when hood is closed Pin #1 is floating. Hood opened make Pin #1 to close on Pin #2, which then triggers the OEM alarm once it is activated.
Therefore, any aftermarket sensor with a negative trigger can be connected to Pin #2:
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To run the wires into the engine compartment I used a passage already made under the steering wheel bulkhead, to the left and above the brake pedal (only DSG, manual transmission GTI need to find another passage):
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Use this Crutchfield wire "fisher" to pass the wire into the engine compartment, it will make your life easier from now on every time you need to pass a wire thru anywhere in the car:
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The DEI motion sensor was installed right in front and below of the DSG lever for better sensitivity:
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As explained before, there is no constant 12V wire anywhere in the GTI that is only active when the car is off, so I used a 5 pin relay to switch -in my particular case- the ACC line output of the PAC CAN steering wheel adapter as the trigger that will switch a constant 12V output to ON only when the car is off. This will be the motion sensor power input...
The relay/sensor wiring is like this:
Relay #86: ACC from PAC CAN or any ACC line found in the fuse box
Relay #85: Ground and Motion sensor Black wire
Relay #30: Constant 12V
Relay #87: Not used
Relay #87a: Motion sensor Red wire
Motion sensor Blue wire: Pin #2 of Hood switch plug
Motion sensor Green wire: not used in this application
http://www.the12volt.com/relays/relays.asp
A perfect installation will require an isolation diode between the motion sensor Blue wire and Pin #2; this will make the motion sensor electrically "invisible" to the hood switch and still work. However, because it is only ground I decided not to use it although I do not encourage it; it's up to you. For more information about blocking diodes check this link: http://www.the12volt.com/diodes/diodes.asp
This should be enough to install not only a motion detector but any other negative trigger sensor to the OEM alarm on the cheap: the price of this DEI 508D is around $5.00, add some wires, a diode, the relay and connectors and maybe you will spend $10.00 plus time... but it works like OEM. Close door, activate the alarm and any hard impact to the body or glass will trigger the alarm. Open door and the sensor is off as soon as the car is started and will remain off as long as the key is in the ignition. http://****************.com/smile/emthup.gif
For the ultimate protection it could be needed a second sensor in the trunk area to better protect the rear hatch. A front sensor can still protect the rear but the sensitivity will be borderline so it will require a bigger impact in the rear than in the front to trigger the alarm. Both sensors can be connected to the same trigger point, but two diodes would be needed to isolate one sensor trigger output from the other.
Good luck! http://****************.com/smile/emthup.gif
Modified by M3Tech at 6:47 PM 5-29-2007
The switch has two wires, Pin #1 and Pin #2. Pin #1 is always grounded thus when hood is closed Pin #1 is floating. Hood opened make Pin #1 to close on Pin #2, which then triggers the OEM alarm once it is activated.
Therefore, any aftermarket sensor with a negative trigger can be connected to Pin #2:
To run the wires into the engine compartment I used a passage already made under the steering wheel bulkhead, to the left and above the brake pedal (only DSG, manual transmission GTI need to find another passage):
Use this Crutchfield wire "fisher" to pass the wire into the engine compartment, it will make your life easier from now on every time you need to pass a wire thru anywhere in the car:
The DEI motion sensor was installed right in front and below of the DSG lever for better sensitivity:
As explained before, there is no constant 12V wire anywhere in the GTI that is only active when the car is off, so I used a 5 pin relay to switch -in my particular case- the ACC line output of the PAC CAN steering wheel adapter as the trigger that will switch a constant 12V output to ON only when the car is off. This will be the motion sensor power input...
The relay/sensor wiring is like this:
Relay #86: ACC from PAC CAN or any ACC line found in the fuse box
Relay #85: Ground and Motion sensor Black wire
Relay #30: Constant 12V
Relay #87: Not used
Relay #87a: Motion sensor Red wire
Motion sensor Blue wire: Pin #2 of Hood switch plug
Motion sensor Green wire: not used in this application
http://www.the12volt.com/relays/relays.asp
A perfect installation will require an isolation diode between the motion sensor Blue wire and Pin #2; this will make the motion sensor electrically "invisible" to the hood switch and still work. However, because it is only ground I decided not to use it although I do not encourage it; it's up to you. For more information about blocking diodes check this link: http://www.the12volt.com/diodes/diodes.asp
This should be enough to install not only a motion detector but any other negative trigger sensor to the OEM alarm on the cheap: the price of this DEI 508D is around $5.00, add some wires, a diode, the relay and connectors and maybe you will spend $10.00 plus time... but it works like OEM. Close door, activate the alarm and any hard impact to the body or glass will trigger the alarm. Open door and the sensor is off as soon as the car is started and will remain off as long as the key is in the ignition. http://****************.com/smile/emthup.gif
For the ultimate protection it could be needed a second sensor in the trunk area to better protect the rear hatch. A front sensor can still protect the rear but the sensitivity will be borderline so it will require a bigger impact in the rear than in the front to trigger the alarm. Both sensors can be connected to the same trigger point, but two diodes would be needed to isolate one sensor trigger output from the other.
Good luck! http://****************.com/smile/emthup.gif
Modified by M3Tech at 6:47 PM 5-29-2007
