difficulty: 1/5
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Introduction
WARNING: The battery contains electricity and acid and can spontaneously explode! Lead acid batteries make hydrogen gas and they can explode, sometimes with no warning, sending sulfuric acid spraying everywhere. Always wear eye and skin protection when handling a battery. Remove or insulate all rings, necklaces, watches, etc., before working near the battery since accidental contact with the positibe terminal and a ground can cause electrocution or serious injury.
The alternator charges the battery which provides the electrical needs of your car. Symptoms of a bad alternator would be the battery warning light coming on, less than 14V at the battery when the engine is running, or dimming headlights when the electrical load is higher than normal (and you know the battery is good). If the battery is weak, engine rpm when starting can be too slow. The engine computer sees this and does not inject fuel. Luckily, the TDI has relatively low electrical load since there are no sparkplugs.
If you are having a charging problem, it's either the alternator, battery, or grounds. The battery voltage when the car is off should be over 12V. The battery voltage when the engine is running should be at least 14V even at idle. It could also be a loose battery terminal or ground that prevents proper charging of the battery. If you are not sure, take the alternator to an auto parts store because many places will check it for free. Many places can even check the charging system on the car.
If you have any questions, please post it in the VW Passat TDI forum in the myturbodiesel bulletin board!
Battery voltage should be about 13.5-14V with the engine running. The system works on 12V and the battery acts like a voltage damper. Do not run the car without the battery. With the engine off, battery voltage should be about 12.5V and no load. With electrical load, voltage should steadily drop to about 9V.
Remove the 1x 13mm bolt holding the battery clamp.
Remove the 1x 10mm nut holding the negative (should be on the passenger side) terminal cable first. Set it aside and insulate it so that it can't accidentally touch anything. Do the same with the positive terminal.
I suggest removing the spring clip above the battery holding the windshield trim to the metal. This will let the windshield trim move a little and make it easier to pull the battery out.
Look for a built-in handle on the battery to help you pull it out.
Installation is the reverse of removal.