Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSAAB1994900 BASE, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)HEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSA/C-HEATER SYSTEM - AUTOMATICDIAGNOSISFAULT DIAGNOSIS
1994 Saab 900 Base, Standard
Fault Diagnosis
1994 Saab 900 Base, StandardSECTION Fault Diagnosis
- Ensure SDA Mk II is connected to Saab ISAT Scan Tester. Connect ISAT Scan Tester to data link connector (under left side of dash, next to steering column).
- During diagnosis, ignition switch should be in normal driving position. Obtain readouts and make a note of stored Diagnostic Trouble Codes (DTCs) in all systems before disconnecting battery and any control module.
- If communication cannot be established between ISAT and the A/C-heater control panel (control module), check that ALL fuses are not blown and that they are supplied with current. Check wiring harness between A/C-heater control panel and data link connector. Also check power and ground circuits to data link connector. Ensure data link connector pins are not damaged.
- Ensure ignition switch is off before disconnecting components, control module, or connectors. DO NOT remove the control module's signal ground without first disconnecting the battery, as this could damage the control module.
- Check power and ground circuits to control module. Ensure component connector pins are not damaged. Never switch from volts to ohms, or vice versa, on multimeter without first having unplugged tester leads.
- Reattach connectors and start and drive vehicle to check whether the fault or faults persists. Voltage values are proportional to battery voltage, and should be used only as a guide.
- All control modules are sensitive to electrostatic discharge and could, if handled incorrectly, be damaged. Avoid disconnecting or removing the control module unless absolutely necessary. After checking functions, always clear fault memory with CLEAR FAULT CODES command.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.