Thought I'd start a thread for common faults and things to look out for when buying an A4. Feel free to add to the list, my list only covers the 1.9 Tdi. My car is Audi A4 B6 1.9 TDI PD 130, AWX - 8 years old, 103k Part -Common Fault -Solution Plenum Chamber Grommets -Plenum Chamber grommets block with silt allowing water to fill the plenum chamber infront of the windscreen. Causes flooding into passenger footwell, ECU, HVAC fan, brake servo. -Remove grommets by removing battery and battery tray. Wiper mechanism seizing -The mechanism that links the motor to the wiper arms can seize up -Remove mechanism and regrease all moving parts Air con regas -Airconditioning system slowly leaks and requires regular regas. Pump fails to operate below a certain gas pressure. -Regas every couple of years. Brake Light Switch -Traction control light comes on when brake pedal is first pressed -Replace Brake light Switch Airbag connector below seat -Airbag connectors below driver or passenger seat cause airbag light to come on -Clean connector and add switch lubricant to connections Speakers crackling -Door connections for speaker wires were manufactured with grease in the terminals which breaks down and causes speakers to fail & crackle -Remove grease from door connectors Rear washer jets block -Rear washer jets block causing washer pipe failure and corrosion within tailgate -Keep jets clean Glovebox hinges -The soft close damper/ glovebox light switch unit becomes stiff putting unnecessary stress on the glovebox hinges -Remove plastic cover on the side of the glovebox and lubricate light switch plunger Worn fuel line -On 1.9 TDI -The fuel line rubs on the underside of the air intake pipe that goes into the EGR valve. Wear occurs because braided protection slides further down the fuel line exposing the rubber. -Reposition braided protection on fuel line and secure with zip tie/ jubilee clip HVAC failure -There are small servos that control the HVAC system which are prone to failure. Motors show signs of failure when the start to 'click'. Defroster flap commonly first to fail. Remove glovebox to access 4 servos including defroster flap. -Replace servo or disconnect whilst open. Coolant Temperature Sensor -Prone to failure and throw an intermittent fault code -Replace coolant sensor Thermostat -Prone to fail overtime and engine can no longer remain at 90 degrees during use. Engine takes a long time to warm up. -Replace thermostat Battery failure -First signs of the battery failing is a brake warning light on the DIS followed by 3 beeps. First occurs during cold weather. A good battery should hold 12.6v, weak battery will be 12.2v or less. -Replace battery Rear Anti roll bars -Anti roll bars corrode, crack the plastic collar which then damages the rubber bush. -Replace anti roll bar and rubber bushes Wiper blades -Clips securing the wiper blade to the arm break. Also plastic hinge piece prone to wear allowing deflector blade to touch & scratch the windscreen. -Replace entire wiper arm as clips are not available separately.