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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

Materials

Automotive cable 14/0.030 (various colours) – about 60m total required, depending on component locations selected. Colours suggested:

• Red     - 10m
• Black   - 10m
• Brown  - 10m
• White  - 2m
• Blue    - 2m
• Green  - 2m
• Purple – 3m
• Purple/White   - 4m
• Brown/White   - 4m
• Pink     - 10m
• Resin-cored electrical solder
• Heat-shrink tubing: 6mm plain – about 600mm required
• 12mm adhesive – about 600mm required
• Self-tapping or Self-drilling screws – (St/Steel self-tapping 8x¾)
• Self-extinguishing Flexible conduit (Polypropylene recommended)
• Flame retardant adhesive electrical insulating tape

Crimp connectors: 

•  Bullet male (red) - 10
• Bullet female (red) - 10
• Scotchlok - 20
• Eyelets – 6mm (red) -10

Cable ties (black nylon)    approx. 20 - 30

General requirements

Do not attempt this job unless you are confident about working on your car electrical circuits, and have a reasonable knowledge of electric principles. If you are in any doubt, get the job done by a qualified professional installer.

Don’t expect to save a bundle of money by doing it yourself. I reckon the total cost of my own installation was about £250. I could have had the same system professionally installed for around £350 - £400, so I saved only £100 to £150 by doing it myself. The advantages for me were that I was able to design the system myself, and get it to my exact requirements, and if the system ever goes wrong, I should be able to fix it quickly myself, without having to go back to the installer.

If you don’t already have a service manual, get one before starting. The Bentley manual is highly recommended, and contains comprehensive wiring diagrams, which are essential when doing a job of this complexity. My only complaint about the Bentley manual, (and it’s a very minor one), is that it has been written for the US market, and often refers to ‘driver’s side’ and ‘passenger side’, which of course mean the opposite on these islands!)

Allow plenty of time to complete the installation. Mine took about a two weeks, (including the design), working most evenings, and one full weekend. (A professional who was familiar with Saabs, by contrast, could probably have completed the job in one day!)

Before you start, decide where you are going to install everything, and sketch out the main circuits, so that you are not ‘making it up as you go along’. Use my wiring schedule as a template, or devise your own, but make sure you document what you do, in the event that you, (or a subsequent owner), needs to repair or modify the system.

Wiring protection

Wherever possible, enclose all the longer runs, (greater than 300 to 400mm or so), of exposed wiring in a protective conduit. I used black 20mm flexible self-extinguishing polypropylene electrical conduit. This is crush resistant, and gives a high degree of protection, but is light and easy to fit. You can either thread the cable through the conduit, or cut the conduit lengthways using scissors, and fit it over the cable after installation.

Particular places where you will probably need conduit are where the cables pass under the carpet next to the central console, and in the engine compartment area.

Soldered joints need to be sheathed for mechanical strength as well as insulated. I used double heat-shrink tubing: an inner sheath for protection and insulation, and an outer, adhesive sheath for maximum strength.

Keep cables tidy by using cable ties to hold them in place; keep the conduit in place using cable ties too.

Wherever cables need to pass through metal, you must use a rubber gland or grommet, to prevent the sharp metal edge from abrading the insulation. This is vital in a car, where constant vibration may lead to rapid wear, and there is the potential for a fire. In most cases, you will be able to feed cables through the existing rubber cable glands.

Installation

First step was to decide where to put everything. The alarm unit itself is very compact, and could be fitted almost anywhere, but I decided to put it under the rear seat, for a number of reasons: first, it’s not difficult to get to; second, there’s space for the immobiliser and any other relays alongside the existing relays here; third, it’s close to the ignition loom, power window, interior lights and sunroof switches, and the wiring loom that carries power to the indicators. Finally, I wanted the immobiliser to break the fuel pump circuit, rather than the ignition, and the fuel pump power cable is conveniently available under the rear seat.

One potential problem about under-seat mounting concerns the range of the remote transmitter: when the unit is mounted in this position, the remotes will only have an effective range of a few metres. You can extend the range by extending the antenna lead of the unit, but if you want maximum range, you may need to consider mounting the unit higher up in the car, so that the shielding effect of the car’s steel body is lessened.

I mounted the alarm control unit using the adhesive Velcro patch supplied – this works well, and avoided having to drill holes in the floor. I mounted the two window interfaces close by, and the relays were attached to the rail next to the existing relays.

If you decide, (as I did), to fit a microwave detector, you need to give some thought about the location of this item. Unlike the other parts of the system, you have few choices, since the microwaves will not penetrate steel. So, if you mount the unit too low, the external detection zone will be limited. The instructions recommend fitting this unit ‘between the front seats’, or in the headlining. The SAAB headlining is notoriously difficult to fix if it starts to sag, so I decide to leave well alone. After some experimentation, I found that if I mounted the microwave unit just behind the rear ashtray in the centre console, I could still get a reasonable external zone: just enough to cause the piezo sounder to beep when someone walks within about a foot of the car. If you want more sensitivity than this, it is possible to adjust both the external and internal zone sensitivity using small pre-sets on the microwave unit.

The location I chose for the microwave unit is also close to my chosen location for the main alarm control unit, which is useful since the connecting leads are quite short, and also means that the microwave unit can be accessed for adjustment without lifting the rear seat. Disadvantage – the rear ashtray either has to be left out, or left permanently open, or modified to make space between it and the console. Either way, if you have smokers as rear passengers, you may have a problem. (Since my usual rear passengers are three Border Terriers, this is not an issue for me!) Other places you could try would be under the dash, (access via the front speaker grilles), or in the centre storage bin (mount it as high as possible). These two locations may mean that you’ll need to extend the connecting cables between the main unit and the microwave sensor.

Access

To make things easier, I removed the passenger seat, and the rear seat, and pulled the carpet out of the way. I also removed the kick panel, to get to the central locking unit, which is mounted on the LH side. (By the kick panel, I mean the padded section that runs across the car, under the instrument panel, at knee height) The kick panel can be removed after first taking out the front ashtray, exposing a single large bolt, which is then removed, followed by removing two smaller bolts at each side from within the small space just in front of the door hinges, (accessed with the bonnet/hood open).

Central locking

Because I wanted full remote central locking, I also had to replace the driver’s side door switch with a motor.  David Mills provided the motor for £7.50 including postage, and kindly gave me detailed instructions for fitting, (thanks David!). This was probably the hardest part of the whole job, mainly because I have quite large hands, and the space in the door is very limited.

The sequence of operations involves first unplugging the existing connector from the driver’s door hinge area (cables are be green/white, yellow & black – access after opening the bonnet/hood). Then remove the door trim and the vapour barrier (either a polythene skin, or a shaped plastic membrane), to give access to the lock mechanism. Unplug the switch at the connector inside the door, and remove it. Then fit the motor, (easier said then done!). Remember to replace the polythene shroud around the motor; (I replaced mine using heavy gauge polythene, cut to shape with scissors). I used the existing cables to wire up the motor, fitting the new motor’s two-pin connector into the existing 3-pin connector by carefully filing away part of the shroud on the two-pin connector. I then fed new cable from the other end of the existing cable, (the one I disconnected earlier), through the bulkhead and up to the central locking unit.

Under-bonnet components

The main siren is fitted close to RH door hinge, on the engine compartment bulkhead; the smaller piezo sounder, (this provides the warning beep when somebody gets too close to the car), is further forward, also on the RH side, close to the windscreen washer bottle and the RH horn; the bonnet switch is mounted on the RH cross member. Because all these items are on the RH side, I was able to pass all the wiring through in a single operation. To do this, I used an electrician’s draw tape, poking it through from the engine compartment until I was able to grab hold of the free end from under the instrument panel. I then fed the cables towards the centre console, and from there to the rear seat area.

I used brown cable for the bonnet switch, red for the positive, black for ground, and purple/white for the alarm trigger.

Ideally, the longer cable runs, (to the bonnet/hood switch and the piezo sounder),  should be protected using flexible, fire-retardant conduit. I used 20mm polypropylene  conduit from Screwfix (www.screwfix.com). You can either feed the cables through the conduit first, or cut the conduit using scissors, and roll it over the wires when they are all in place. The conduit should then be attached to the bulkhead at intervals using ties.

Immobiliser

The Microscan alarm that I used has an optional immobiliser relay. Instead of using this to cut the electrical circuit to the ignition, I decided to use it to cut the fuel pump circuit. I did this for two reasons: first, even if a thief manages to ‘hot-wire’ the car, he still won’t get far without the fuel pump. Second, the fuel pump supply is, conveniently, right under the rear seat.

By the way, in case you are wondering how far the car will travel without the fuel pump, the answer is ‘not far’. Without the fuel pump, the car may just manage to start, but will cut out almost immediately. If you cut the pump circuit while travelling at 30mph, the engine will only run for a second or two before cutting out.

It’s a good idea, when fitting the fuel circuit immobiliser, to use shrouded bullet connectors to connect the relay terminals; this way, if you ever need to disable the immobiliser, you can do it by removing the

 

NOTE: if you have a window closure interface, or sunroof closure, wire the yellow trigger to the last daisy-chained interface trigger.

With thanks to Richard Mcbride, for writing & supplying this comprehensive article.

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