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 MANUALSAUDI1996A4 BASE, STANDARDREPAIR AND DIAGNOSISHEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSA/C-HEATER SYSTEM - AUTOMATICTESTINGA/C-HEATER CONTROL PANEL
1996 Audi A4 Base, Standard
A/C-Heater Control Panel
1996 Audi A4 Base, StandardSECTION A/C-Heater Control Panel
- Put DVOM in 20-volt range. Using Adapter Cable (VAG 1598/12), use DVOM to check voltage between Test Box (VAG 1598) terminals No. 9 and 14. Turn ignition on. If about battery voltage does not exist, check Black/Blue or Brown/Blue wire between fuse block and A/C-heater control panel. Check Brown wires between A/C-heater control panel and ground. Repair as necessary.
- Check voltage between test box terminals No. 9 and 15. Turn ignition on. If about battery voltage does not exist, check Brown wires between A/C-heater control panel and ground. Repair as necessary.
- Put DVOM in 200-ohm range. Using Adapter Cable (VAG 1598/11), use DVOM to check resistance between Test Box (VAG 1598) terminals No. 49 and 52. If resistance is not less than 20 ohms, check Brown wires between A/C-heater control panel and ground. Repair as necessary.
- Put DVOM in 20-volt range. Using Adapter Cable (VAG 1598/12), use DVOM to check voltage between Test Box (VAG 1598) terminal No. 13 and ground. Turn ignition off. If about battery voltage does not exist, check Red/Blue wire between fuse block and A/C-heater control panel. Repair as necessary.
- Check voltage between test box terminal No. 7 and ground. Turn ignition on. Turn parking lights on. If about battery voltage does not exist, check Gray/Green or Gray wire between headlight switch andA/C-heater control panel. Repair as necessary.
- Check voltage between test box terminal No. 7 and ground. Turn ignition on. Turn parking lights off. If less than 2 volts does not exist, repair short to power in Gray/Green or Gray wire between headlight switch and A/C-heater control panel.
- Check voltage between test box terminal No. 45 and ground. Turn ignition on. Turn parking lights on. When illumination rheostat is turned, voltage should fluctuate between zero and 12 volts depending on setting. If voltage is not as specified, check Gray/Green or Gray wire between headlight switch and A/C-heater control panel. Repair as necessary.
- Check voltage between test box terminal No. 45 and ground. Turn ignition on. Turn parking lights off. If less than 2 volts does not exist, repair short to power in Gray/Green or Gray wire between headlight switch and A/C-heater control panel.
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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.