Class III Alarm (Getronix) installation

(Project by Leo de Goede)




5 parts of the alarm unit



Elevation Detector,

LED and Radar

Special supports should be constructed to mount the parts. These may be installed in the car without drilling holes in the firewall or in the dash.


Soldering Iron,

Cable-Shoe Tweezers,


Some Wire and Insulation Tape.


No drilling of any visual parts of the barchetta.

No new holes in the firewall to pass wires from the inside to the engine compartment. Connectors in alarm-wires to enable dismantling without knowledge of the circuitry.





Remove the painted covers underneath the dash at the driverıs side and the passengerıs side (3 pieces).
The Siren is mounted on a bracket that is clamped under the battery tray. This requires removal of the front battery clamping screw. Underneath, two bolts are located that may be loosened 3 turns. After this the tray can be lifted upward and a tooth-shaped siren support may be slotted into the open gap. This is the same place where the original Fiat alarms are mounted. The support is welded and shaped from 2mm steel strips to make it nice and sturdy.
The main unit (CPU) is mounted in the passenger compartment by using two of the three bolts that hold the Hitachi control unit. The metal support of the Hitachi remains as it is, and the support of the alarm fits under the two nuts. An advantage is the good ground that is provided for the Hitachi. The CPU-support is welded and placed to avoid contact with the passengerıs shoes. The dipswitches face downward and remain visible (that is, when you lay on the passenger floor Š).
The elevation detector is mounted in the engine compartment on the bracket, which supports the brake fluid container.
The LED that was initially installed for no purpose in a barchetta without the factory alarm is used for this alarm. The end of the 20 cm of wire that is connected to the LED is taped underneath the plastic cover that holds the ashtray. To remove this cover, first lift the gear-lever cover and then loosen the four screws that appear. By lifting and pulling backward this cover is removed sufficiently to install the radar unit. The advantage is that no drilling is required. This LED has already a serial resistor. Polarisation is not critical; just try it.
The radar unit ³looks² through the ashtray upward with a slight inclination towards the back. Make sure the potmeter and LEDıs on the unit are reachable after the lever-cover is pulled. The bracket, on which the radar unit is placed, is mounted to the metal edge that is visible in the lever compartment. Since drilling is under an angle, it is better to use a mini-drill.
(see diagram below after reading steps 7 to 17)
The bundle from CPU to the fuse box left of the driver is guided over the heater-unit along the firewall. This distance is greater than expected. Proper labelling of the wires avoids confusion.
The wires from the LED and the Radar unit are guided inside the central dash and come out at the left foot of the passenger. From here they go upward and pass along the fuse box located near the passengers glove box / airbag.
The antenna is lengthened and fed through the right front side trim of the windshield. To avoid it slipping down again, it is fixed high inside the inner compartment light.
The bundle from the inside to the engine compartment is minimised, to enable the use of the existing cable-bridge. This bridge is found behind the clutch where the bonnet release cable passes through the firewall. In the rubber bridge, a spare rubber pass is available for the alarm wires. First cut the top away, from the engine compartment.

The unit has command wires to close and open the electric door-locks (when fitted on the barchetta). To locate the corresponding barchetta-wires, follow the bundle that leaves the driverıs door and enters the body. Inside, behind the fuse box, this bundle ends in a connector. At that spot it is easy to make two taps.

Make sure the cables behind the drivers fuse box are fixed in a position high enough to keep them clear from the left foot of the driver.
Please do not use ready-to-clamp connectors to make taps on the existing wires. During installation and manipulation the fine copper wires inside may break. It is far better to remove insulation by burning with the soldering iron over 1 cm and after removing the insulation, a suitable place is created to wind the tapping wire around and solder.
The ground-connection in the engine compartment is made at the point where the bonnet-ground is screwed to the inner fence.
The bonnet switch must be protected against unauthorised operation through the gap. Screwing a cap to the bonnet that falls over the switch when closed does this.
The engine immobiliser that comes with the alarm may be installed if you wish.
Some final advice: use some cable covers (tape) to protect wires from been damaged by sharp edges over time, under the dash for example.
After installation, the real fun begins. It is much more rewarding to do it yourself and to enjoy the meticulous way you did it. You will soon forget about the effort it tookŠŠ.




Wiring diagram for the installation of a class III alarm from Getronix with radar unit, elevation detector and remote door lock control.