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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

I recently installed an alarm system in my 1990 Classic 900, and thought I could pass on some tips to others who might want to do the same thing. I live in the UK, so my experience will be more relevant to other UK owners, but the general principles apply anywhere of course.

The alarm

The alarm system I chose is a Microscan 424, supplied by Direct Car Parts ( – highly recommended for good technical advice and speedy delivery. The Microscan helpline is also excellent for more detailed technical information.

The Microscan 424 costs £90, (incl. UK delivery), and for this you get a remote alarm, (using frequency hopping codes to defeat thieves with scanners), a central-locking interface which works with the C900 system, a two-stage shock sensor, and a dual-zone microwave detector. Two remote transmitters are included. For those who want an immobiliser, there is an optional relay, enabling you to cut power to the ignition, (or any other circuit), when the unit is armed. Also available are interfaces to power windows and sunroof, so that if any of these have been left open, they will close when the system is armed. (I find this particularly nice!).

By the way, the reasons I went for the microwave, (as opposed to ultrasonic), interior protection were: first, the microwave unit is easier to install, and second, it provides exterior protection as well – useful if you want to warn off kids or drivers of supermarket carts!

The package I bought included the basic alarm, the immobiliser relay, and two window interfaces. (One window interface controls the left and right windows of my 3-door, and the other operates the sunroof. If you have a 5 door, you will need three of these units to control all 4 windows and the sunroof.) With these options, my total bill was just over £140. This gave me a remote alarm, with central locking, dual-zone protection, and automatic total closure.

The Microscan unit also includes a facility to switch on the interior lights when the unit is disarmed. To use this, I hooked up a standard automotive relay (obtained from Autosparks ) for £3.28 including connector. Autosparks also supplied suitable cable for wiring everything up, as well as grommets, blade connectors and heat-shrink. Total cost for these was £28. You can get all this stuff from your local car parts shop, or Halfords – there’s nothing really special required, except maybe the coloured wires, which I tried to match up to the Saab loom colours wherever feasible.


You will need some basic tools for the installation. Some are more essential than others.

Additional (nice-to-have) tools:

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