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Rear Radar Detector Installation

This article will describe how I installed a Bel 980 unit behind the rear radiator grill of a Diablo. I relocated the speaker up forward to a position right behind the drivers seat. The Bel circuit board is removed from its plastic housing and placed in a watertight plastic box.

Again to state the obvious. What I will describe involves opening up and seriously modifying a Bel 980 radar detector unit.  You will void the manufactures warranty and can quite easily render the unit useless. If you are not good with your hands, have never done any electrical wiring and soldering, do not attempt this procedure. Get help from a friend.

Figure 1. Rear radar detector behind Diablo radiator grill frame.
Radar Detector Position.  As in the case of a front facing radar detector there are a number of locations one could place a radar detector facing backwards in a Diablo.  The simplest option would be to simply attach the unit to the rear window behind the drivers seat.  I found this to be somewhat unsatisfactory for two reasons.  First the unit is very visible and open to been stolen. More importantly I found it not to be very sensitive to radar signals. For a radar signal to reach it, it has to travel under the rear wing/spoiler up over the engine area and into the cabin area. This appears to lead to a weak signal.  I decided to place the unit behind the radiator grill at the back of the car as shown in Figure 1. It is important to place the unit on the extreme right hand side beside the tail lights. The central region of this grill gets very hot and could damage the unit. 

Please read a description of front radar placement before proceeding with the installation of a rear facing unit. As before take care that the speaker leads do not short against the Bel circuit board.

Unlike the case of the forward facing unit, the rear unit is exposed to the outside environment and thus has to be made waterproof. The approach I used was to place the circuit board of the Bel 980 unit in a custom plastic box (1" X 3" X 5" in size). In the side of this box was cut a hole such that the LED display could be pushed through. 

Power Connection.  A second hole was made for a single 4 conductor cable.  The red and black speaker wires connected to the circuit board were removed and two of the above four leads from the above cable were soldered to the board.  The four conductor cable should be at least 20 feet in length. The Bel units speaker is soldered to the same pair of leads at the other end of the wire.  Test the speaker is working by applying power to the unit.  

Next we need to hookup the two remaining leads of our four conductor cable to the 12 volt power supply to the unit.  We need  to make sure the +12 volt supply goes to the internal ring of the radar power plug and the ground lead goes to the outer ring of the connecting plug.  Make absolutely sure you get this right.  Before you cut off the cigarette socket plug from the power wire, plug it into the car. Determine which is + and which is ground on this small plug using a volt meter.  Write these down and store. You can solder the leads directly to the circuit board or to the plug socket lead. The latter takes up less room in the box but requires a slight knowledge of circuit board layouts and a volt meter.  In any event again check the unit is functioning by applying power to the unit.  The sound and LED display should work. 

Now we need to configure the unit to "Auto scan" and "Quick Start" modes. Please read the Bel manual for details as to how to do this.  When you are sure you have things configured correctly you can then seal the unit in the box using plastic glue. It is essential the whole setup be completely waterproof. In particular seal areas around the LED display and where the cable comes out of the box.  Figure 2 shows a unit ready for installation.

Figure 2. Waterproof custom box containing rear radar detector unit. Note LED display. Figure 3. Top view of radar detector installed in Diablo. The unit is glued to frame on two sides. A metal support is also used.
The box is light and so does not need much structural support to be held in place. I used a little epoxy glue on two sides to bind the box to the frame of the car as shown in figure 3.  As a safety measure I also bolt it in place with a metal bracket also shown in figure 3. I use metal screws to attach the bracket. Take care to position the screws over the box so they do not make contact with the circuit board inside. This would be a good time to test the unit is still functional. Connect up a +12 volt lead and ground to the end of the cable.  The LED should say "Auto Scan" and the speaker should beep once.
Laying Cable. Now comes the fun part. We need to run the 4 conductor cable from the back of the car across under the heat shield at the back of the car, over the air filter duct and wheel, down beside the engine, along the central drive bar shaft area, around and in through the brake peddle compartment area of the car, along the inner floor , up to and under the seat where a 12 volt supply and switch described in the front radar detection article  is available. Everybody will have their own way of doing this. It is important to remember the engine compartment of Lambos gets very hot. Care has to be taken to strap the wire down all along the way keeping it away from hot metal surfaces. Also the drive shaft rotates at high speed under the car. The wire needs to be bound at multiple points along its length to make sure it does not flop around and catch in this shaft. Getting to this shaft will involve temporally removing two panels on the underside of the car.  Rather than describe each step I include a set of pictures that I think illustrate the route.


Figure 4. Cable is run between heat shield and frame Figure 5. Cable comes out other side of muffler heat shield Figure 6. Cable is run over air filter intake
Figure 7. Cable is carefully run down outside engine heat shield. Note tie-downs Figure 8. Cable is run beside clutch leaver. Note tie-downs. Figure 9. Cable is run along drive shaft. Note numerous tie-downs
Figure 10. Cable is carefully tied down away from front differential unit Figure 11,  Cable is put through front firewall. A hole is drilled. Note do not damage bake lines Figure 12. Final position of cable. Cable ends at switch and 12 volts. Note also, one Amp inline fuse.


For 6.0L Diablos and presumably later cars there is no rear grill like the one described above through which the radar detector can be placed. In these situations the best solution is to attach the detector below the scar as shown in figure 13.  It is important however to be sure the whole unit is completely waterproof in this position.
Figure 13.  Position of rear detector in 6.0L Diablo  


This page was last modified on 03/12/2014

This page was last modified on 09/06/2014