Alternators have superseded generators on Volkswagen (VW) vehicles as they are more reliable, have fewer moving parts and produce greater output at lower revolutions. However, many older VW vehicles have generators fitted so if you are noticing your battery isn't charging properly, or your headlights are dim then test your VW generator to ensure its producing the correct voltage. You can easily and quickly test your VW generator using a multimeter.
Find the range of voltage your VW generator produces, if it's working correctly. Get this information from the owner's manual. You can find it in the specifications section at the back of the manual. If you don't have a manual you can usually download a free manual for your model of VW on the internet. The average voltage is either 6 volts or 12 volts, depending on the age of your VW. If the average is 6 volts the range is 4 to 8 volts and if it's 12 volts the range is 10 to 14 volts.
Access the VW battery. This can be found under the hood or in the trunk, depending on the model of your VW. For example, a VW Beetle has a rear mounted engine, but the battery is in the front luggage compartment. Turn on the engine of your VW.
Use a multimeter and set it to read volts. If the meter has variable voltage ranges set it to read between 0 and 10, if the generator output range is 4 to 8 volts. If the generator output range is 10 to 14 volts set the meter in the range 5 to 20 volts.
Connect the wires from the meter to the battery terminals. Some meters have small metal spring clamps on the ends of the wires; others have metal sensors that you simply place on the battery terminals. Connect the metal clamp or metal sensor, on the end of the red wire onto the positive battery terminal. It's clearly labeled "+" or "Pos." Connect the metal clamp or metal sensor, on the end of the black wire onto the negative battery terminal labeled "-" or "Neg."
Check the voltage reading produced from the VW generator on the meter display. If the voltage output is in the range you noted earlier, your generator is working correctly. If it's below the lower figure in the range or above the highest figure in the range you need to get the generator checked out as it's either not producing enough electricity to charge your battery and electrical equipment, or is producing too much electricity which could damage your electrical equipment.
