This document is not intended as a step-by-step guide to repairing your A/C.  Rather, it’s a rundown of various legal, environmental, and practice considerations which are important in tackling the process.  Between various laws, questionable marketing practices, and the “mystique” that surrounds modern A/C repair, I found it very difficult to get straight answers when it came time to rebuild my c900’s system.  I’m hoping that by producing this document, others don’t have to spend all the time I did researching these concepts.

With the introduction of the 16v engine, Saab switched from Bosch CIS injection (a type of mechanical fuel injection) to fully electronic Bosch LH (for Lambda-Hotwire) injection.  Bosch LH injection incorporates a hotwire-type airflow measuring device, an oxygen sensor for emissions control, and electronically controlled, batch-fired fuel injectors. 

Saab employed two basic varieties of Bosch LH injection - version 2.2 on 1985 through 1988 16v turbos and 1986 through 1987 16v non-turbos, and LH 2.4 on 1989 through 1993 16v turbos and 1988 through 1993 16v non-turbos.  (Note:  A subrevision - LH 2.4.2 - was employed on 1991 through 1993 non-turbos with the 2.1l engine - this document does not cover 2.4.2)

Although both versions of LH function in approximately the same way, version 2.4 includes a number of useful improvements:

1. Self-calibrating Air Mass Meter -  On startup, the 2.4 air mass meter (AMM) runs a self-calibration to adjust for age and wear.  On earlier versions, this adjustment was made manually with a trim screw, and required the use of several specialized tools (including an exhaust gas analyzer) to be done properly.  The self-calibrating AMM results in longer functional life and improved emissions.
   
2. True Automatic Idle Control - Early versions of LH fuel injection relied on a throttle plate adjustment to set base idle, and employed the automatic idle control (AIC) valve only to correct for engine load which affected idle speed.  LH 2.4 uses a fully automatic idle control system, including a "last position" memory to enhance idle after startup.  This design results in a more reliable idle and a more reliable AIC valve.
3. Improved diagnostics - LH 2.4 incorporates a number of component self checks and self-diagnosis to help isolate running problems.
   

It is not terribly difficult to install an aftermarket alarm system in the car.  Fortunately, Saab doesn't do anything strange with their electronics to make doing so prohibitive, so don't listen to the guy at Circuit City when he tells you that your Saab requires anything special.  After installing a few of these things, my advice is that if you're reasonably good with a wrench and have a good working knowledge of basic car electronics, save yourself the money and do it yourself.  For me, the only incentive I needed was not having to worry about some minimum wage teenager traipsing around my baby's wiring.