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Audi A4 Voltage Regulator Replacement
 
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Pelican Technical Article:

Audi A4 Voltage Regulator Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$120

Talent:

**

Tools:

15mm, 13mm socket, Philips head screwdriver

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New voltage regulator

Hot Tip:

ALWAYS disconnect the battery before beginning

Performance Gain:

Car charges again

Complementary Modification:

Change drive belt

The alternator charges the battery and provides your car with a constant source of electricity while the engine is running. The voltage regulator does just what it says: it regulates the voltage from the alternator. If there is acid leaking from the battery there is a very good chance the regulator has failed and the alternator is over charging the battery.

Your battery should read a little more than 12 volts with the engine off. To begin inspecting your electrical charging system, inspect the belt that drives the alternator. Is it tight and optimally turning the alternator? If not, then check that the belt tensioner is working correctly. Modern belts seldom break, but they get brittle and glazed with age, and can slip on their pulleys. Replace the belt with a new one as required.

The next item to check is the voltage at the battery. Before performing any tests of your alternator, charge and test your battery. If the battery is faulty, your alternator tests will not be accurate. Next check the voltage of your charging system under load. The voltage should be within 13.2: 14.5 volts d/c. To load, have the engine running at idle, turn on the headlights and the HVAC blower motor. Never disconnect a battery cable while the engine is running to test the alternator. You may cause damage to the alternator or other electrical components from the surge in amperage. If your battery appears to be leaking, then your voltage regulator has probably failed. The battery will usually only leak acid if it has been overcharged at a much higher voltage. If the voltage measured at the battery is more than 14.5 volts when the engine is running, then the voltage regulator is probably bad. If your battery has boiled over and has acid overflowing out the top, make sure that you clean up any spilled acid immediately. Dousing the area with a water and baking soda solution should help considerably to neutralize the acid, and prevent it from eating away at the metal.

A large amount of the time when there is an electrical problem with the charging system it is the voltage regulator, yet people just swap out the entire alternator because it comes with a new voltage regulator included because it is easier, fixes the problem and most people do not understand how the electrical system works on their car. If your electrical issues are caused by a faulty voltage regulator you can save your self a lot of money by just replacing the defective part.

You will have to take the alternator out of the car to replace the voltage regulator. Please see our article on replacing your alternator. You must perform this work first.

With the alternator out of the car take it to your work bench and turn it over.
Figure 1

With the alternator out of the car take it to your work bench and turn it over. There is a plastic cover over the back that is held in place by a 13mm nut (red arrow) a 15mm nut (yellow arrow) and a Philips head screw (green arrow). Remove these fasteners and remove the plastic cover.

The voltage regulator is on the upper section of the alternator and can be removed by removing the three Philips head screws (red arrows).
Figure 2

The voltage regulator is on the upper section of the alternator and can be removed by removing the three Philips head screws (red arrows).

Slip the voltage regulator up and out from the alternator (red arrow).
Figure 3

Slip the voltage regulator up and out from the alternator (red arrow).

There are two metal arms that extend down from the voltage regulator and make contact with the poles on the alternator (red arrows).
Figure 4

There are two metal arms that extend down from the voltage regulator and make contact with the poles on the alternator (red arrows). These arms are held to the alternator by spring pressure. The arms should slide easily back and forth into the regulator. The arms will wear over time. If the arms are worn down, the springs are not working or there is deep corrosion or grooves you must replace the voltage regulator.

While the regulator is out make sure you check the condition of the poles (red arrows) on the alternator: they can be discolored but should not be excessively worn, corroded and should not have grooves worn in them.
Figure 5

While the regulator is out make sure you check the condition of the poles (red arrows) on the alternator: they can be discolored but should not be excessively worn, corroded and should not have grooves worn in them. If the poles are seriously corroded or have deep grooves you will need to replace the alternator. The poles illustrated are fine. Installation is the reverse of removal.

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