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Classic Saab 900: DIY car alarm system 1 2 (3)
DIY alarm system for Classic Saab 900 ( - 1993)
Thanks to Richard Mcbride, for writing & supplying this comprehensive article.
Installation pictures | Wiring instructions
One LED or two?
The alarm is provided with a single red LED, which is used to indicate the alarm status, (off, alarmed, activated, etc). The suggested mounting location, (and the normal one for Saab 900’s, is on the dashboard, or one of the front speaker grilles, but I wanted to use two LED’s, one on each door, next to the lock pull. After speaking to the Microscan technical help-line, I decided to use two high-brightness red LED’s. The supply voltage from the alarm to the LED circuit is 5V, and my chosen LED’s draw a maximum of 30 mA each, so a series resistor is needed to drop the 5V down to the LED operating voltage of 1.8V. The calculation is quite easy, but there is a useful page at http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm which enables you to enter the values in boxes and calculate the resistor needed. (Note however, that this site assumes that you are placing the LED’s in series, whereas it is much easier for this application to connect them in parallel. You need to multiply the current rating by the number of LED’s, and enter ‘1’ in the ‘Total LED’s’ box. Depending on the type of LED’s you use, the brightness you want, and the number you use, the resistor should be between about 50 and 500 Ohms. (I used a 430 ohm resistor to feed two 1.8V LED’s.)
I bought the LED’s from Maplin Electronics, but you may be able to get them from your local Tandy store. You will need a bezel – I used 3mm LED’s, with a matching black bezel. This needs an 8mm hole, which is fine for mounting in the doors. You can solder the wires on to the LED on the bench, and feed them through the hole as a complete unit. (Make sure to insulate the leads – I used 3mm heat shrink around each lead, and then wrapped both leads with a short section of 6mm adhesive heat-shrink, making a pretty robust assembly. Be careful when soldering the leads not to get the LED too hot. The negative lead (cathode), usually has a shorter lead, and is indicated by a flat on the body.
To mount the LED in the door, first remove the exterior trim and the vapour barrier; (on the driver’s door, you will already have done this to fit the lock motor). Drill the 8mm hole next to the lock button, feed the LED with its wires through from underneath, leaving about 600mm free, and fit suitable crimp connectors to the ends. These will be used to mate up with new wires fed in via the door loom.
Feeding the wires into the doors requires an electrician’s draw tape, (or a length of stiff cable). Start by opening the door. Find the rubber shroud that protects the cable loom as it passes into the door, and gently pull it back, exposing the wires inside. Then open the bonnet/hood, and find the cable loom that passes into the door hinge area. Feed the draw tape into the rubber shroud until it appears at the place where you pulled the shroud back. Then feed the tape into the door itself, until it appears inside the door. Attach suitable automotive cable to the draw tape, and pull it through into the engine compartment.
Now you need to feed the cable into the area behind the instrument panel.
Total closure circuits
One of the most useful features on modern cars is the ability to use the alarm remote automatically to close any open windows, or the sunroof, when you leave the car. Some alarms include such a ‘total closure’ circuit, but it will only work on cars that are suitably equipped. Since the classic 900 does not have such a circuit, you have to provide this facility in some other way, and Microscan provide separate units for this. You will need one such unit for each pair of doors, plus an additional unit for the sunroof, (if you want to ensure that your electric sunroof is automatically closed too).
The window closure interface must be wired into the circuit so that it closes the window. I did this by locating the ‘UP’ wire at the centrally mounted window switches. Then I used soldered joints, (wrapped with heat-shrink), to connect the interface to the window circuit, and cut the wire between the two connecting points. (This is all described in the Microscan installation manual.)
The Saab uses the standard ‘Reverse Polarity, rest at ground’ wiring for the power windows.
For the sunroof, the same approach is used. You will need to locate the wire that is positive when the sunroof is closed. On my car, this was a red cable at the sunroof switch in the centre console. As with the windows, you need to cut this wire, and connect the wires from the interface across the gap.
The window interface trigger wire is connected to the alarm trigger output. The sunroof interface is wired, like a daisy chain, to the trigger output of the window interface. Finally, the immobiliser input trigger is wired to the sunroof cascade trigger.
Other options
With the Microscan, (and most other alarms), there are several installation options. Decide on these before installation, since it is much, much easier to select for them before the unit is fixed in place.
Auto (Passive) Arming
Select this option to automatically arm the alarm 30 seconds after the ignition is switched off and the driver’s door closed.
Auto (Passive) Locking
With this option, when the system arms passively, the doors will also lock. If the total closure interfaces have been installed, the windows and sunroof will also close.
NB: if you choose this option, never leave the keys in the ignition when you leave the vehicle!
Anti-hijack (Auto locking)
This option locks the doors a few seconds after the ignition is turned on, and unlocks them as soon as it is turned off. If you use this option, you may wish to provide manual locking/unlocking, by using a separate centre-bias switch in the centre console. (If you have a 3-door like mine, you could what I did, using one the empty rear power window on/off switch slot.)
Auto Re-arm
With this option, if the passive arming is selected, the system will re-arm 30 seconds after disarming if the ignition is not switched on during this period.
Interior light delay
If selected, the interior light will come on for 30 seconds after the system is disarmed – useful in a car park at night. This option needs an additional 12V relay.
Permanent chirp delete
This option disables the chirp on arm/disarm.
Suppliers:
|
Components |
Name/web |
Part Numbers |
|
Alarm |
Direct Car Parts |
AN434 (Alarm) |
|
Wiring, heat-shrink, relay |
Autosparks |
C114 (Cable) |
|
Driver’s door lock motor |
Second-hand |
-- |
|
LED’s, heat-shrink, miscellaneous electronic components: |
Maplin Electronics |
M430R (430 ohm resistor)** UK19 (Red LED 5mm) |
|
Fasteners; |
Screwfix |
14452 (St/Steel self-tapping 8x¾) . |
|
Flexible Conduit (slit) |
Frost Auto Restoration |
E183 Slit Tube 19mm (sold per metre) |
**Use whatever value of resistor you need for your chosen LED or LED’s. If using the LED supplied with the alarm, you don’t need a resistor at all.
With thanks to Richard Mcbride, for writing & supplying this comprehensive article.
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