I have an Audi Avant A4 2002 car which came with a different navigation system.

ANSWER : Hi there. What I suggest is removing the navigation system from your dash and look at the back of the system. There will be a serial number that you can use to locate the type of navigation system that the vehicle came with. If your system is not working, this will help you with a replacement system. If you need further assistance with removing the navigation system from the dash, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : Hello. If the theft light is coming on then it is causing the vehicle not to start. Most of the time the issue is caused by either the key failing or the key sensor located in the key lock cylinder. There is a small chip in the key that provides resistance value to the computer to tell it that the correct key is being used. If there was a spare key I would see if that works. If it does not then it is the sensor in the key lock cylinder. Most of the time the wires from the key lock cylinder break and cause this. It can also be caused by the theft module but that is not as common. If you need to have this problem repaired, consider YourMechanic, as a certified mechanic can come to you to [diagnose why the vehicle will not start] https://www.yourmechanic.com/services/car-is-not-starting-inspection

ANSWER : Hi there. What had happened is the wrong key set the security to the vehicle. This is to prevent the vehicle from starting with the wrong keys. Try removing the battery cables (+) and (-) for 13 minutes. During that time, put the original key in the ignition and turn it on. Activate everything in the car even though there is no power. Then remove the key and hook up the battery cables. The computer should have reset and reset the security. If the security is still being tripped, then I recommend seeking out a professional, such as one from Your Mechanic, to help you

ANSWER : Hi there – Your symptoms describe the behavior to expect when your clutch hydraulics go out (clutch master and clutch slave cylinders). Check your clutch fluid level – it may be low. If the fluid level is low, this usually means your clutch slave cylinder has worn out, not unusual with your mileage, and should be replaced. I recommend a malfunctioning clutch inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

ANSWER : When the charging system or battery light comes on, that is an indication that the alternator is not charging. The battery is in place to start the vehicle. Once running, the alternator provides power for the electrical needs of the vehicle, from spark to the spark plugs to lighting. If the alternator or regulator fail to provide power, the electrical demands will be met by the battery until it is drained. Once that happens, the vehicle will not run at all. The smoking can be from the alternator failing either due to the bearings seizing or an internal electrical short. Also, the serpentine belt or belt tensioner may have failed. If the bearings in the belt tensioner are seizing, the belt may not spin fast enough, start smoking from the added friction, or break entirely. If the belt breaks, then the alternator, water pump, a/c compressor, and power steering pumps will not turn as well. Have a certified technician inspect the vehicle before driving it any further to avoid engine or electrical damage.

ANSWER : Hi there. Check the battery cables and make sure that they are tight and clean. Then check the battery voltage and see if it has a voltage of 12.6 or 12.4. If the battery is less than that, then the battery needs charged. If the battery has 12.4 volts or higher, then place a load tester on the battery and see if the battery can hold a charge when a load is applied. If the battery drops under 9.6 volts, then the battery is no good and needs replaced. If the battery drops to 11.5 volts, then there is a dry cell and possible a burned cell and the battery needs replaced. If you need further assistance with testing your car battery, then seek out a professional, such as one from Your Mechanic, to help you.

ANSWER : Hi, thanks for writing in. It sounds like your battery has crashed. When the system voltage drops below a certain point, the electronics go haywire. The alternator is supposed to maintain the battery voltage at around 14 volts, and I’m guessing that your’s is not working. When the alternator stops charging, the car can continue to run on stored energy in the battery for a few hours, until the voltage falls below about 10 volts, then all those crazy things start happening.

It’s hard to say without hearing it, but the "airplane" noise may be coming from your failed alternator. I don’t recommend running out and buying a new alternator right away, the battery needs to be fully charged or replaced so that you can have a proper tests performed.

Charging or installing a battery, or even jumping one off, is a risky business on a modern car. Connecting the cables incorrectly for even a moment can do a lot of expensive damage to the various modules in your car.

I would recommend having an expert from YourMechanic come to your home or office to confirm a diagnosis on the issue and make or suggest the necessary repairs or replacements.

ANSWER : Prior to buying any car, drive the car around and listen for any noises. Then do an inspection on the vehicle to make sure that it is safe to drive. All cars will need maintenance, but if the car was kept up, then the maintenance should be to a minimum.