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How to Replace Your Audi A4 Alternator
 
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Pelican Technical Article:

How to Replace Your Audi A4 Alternator

Steve Vernon

Time:

2 hours2 hrs

Tab:

$420

Talent:

**

Tools:

6mm Allen, 13mm socket

Applicable Models:

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

Parts Required:

New or rebuilt alternator

Hot Tip:

ALWAYS disconnect the battery before beginning

Performance Gain:

Car charges again

Complementary Modification:

Change ribbed belt

The alternator charges the battery and provides your car with a constant source of electricity while the engine is running. Over time, the alternator will begin to fail and cause trouble with the various electrical devices in the car. If you suspect alternator trouble, you need to check to see that it is operating correctly and is indeed the cause of the problems with your charging system. Sometimes bizarre electrical problems can be caused by a number of faults other than the alternator. It's important to troubleshoot the system prior to replacing your alternator.

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. This should read a little more than 12 volts with the engine off. 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 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.

An important item to check on your car is the engine ground strap. The engine is electrically isolated from the chassis by rubber motor mounts. If the engine ground strap is damaged or disconnected, you will have problems, including electrical system malfunctions, no and/or difficult starter cranking.

If you've checked all of these things and you still have charging problems, it's likely that the alternator will need to be replaced.

You will need to remove the drive or accessory belt as well as move the lock carrier to the service position. While I have heard of people replacing this alternator without moving the lock carrier to the service position you would need to drain some coolant and remove the upper coolant hose. I recommend you move the lock carrier as it makes the job much easier. Please see our articles on accessory belt replacement along with front bumper removal and moving the lock carrier to the service position.

Slide open the battery cover and disconnect the ground strap from the battery terminal (red arrow) and place the cable where it cannot accidentally come in contact with the battery while working, otherwise you will be working around live electric wires.
Figure 1

Slide open the battery cover and disconnect the ground strap from the battery terminal (red arrow) and place the cable where it cannot accidentally come in contact with the battery while working, otherwise you will be working around live electric wires. If you happen to touch the lead going to the alternator against something, you can cause permanent damage to the electrical system if the battery is hooked up. Be smart here and disconnect it. For more information please see our article on battery replacement.

With the lock carrier in the service position use a 17mm wrench and rotate the tensioner clockwise (red arrow) to the open position and insert the locking key or a 5mm Allen to keep it open (yellow arrow).
Figure 2

With the lock carrier in the service position use a 17mm wrench and rotate the tensioner clockwise (red arrow) to the open position and insert the locking key or a 5mm Allen to keep it open (yellow arrow). Slip the belt off the alternator (green arrow).

Some people have had success with draining the coolant from the reservoir (yellow arrow) until it is below the coolant hose (red arrow) and then removing the hose.
Figure 3

Some people have had success with draining the coolant from the reservoir (yellow arrow) until it is below the coolant hose (red arrow) and then removing the hose. If you have moved the lock carrier to the service position you do not need to perform this work.

Use a 6mm Allen and remove the four bolts holding the alternator in place (red arrows).
Figure 4

Use a 6mm Allen and remove the four bolts holding the alternator in place (red arrows). Note: the coolant pipe has been removed for photographic purposes.

Slide the alternator forward and release the clip on the wiring connection (red arrow) and separate the connection.
Figure 5

Slide the alternator forward and release the clip on the wiring connection (red arrow) and separate the connection.

Use a 13mm wrench and remove the main strap (red arrow).
Figure 6

Use a 13mm wrench and remove the main strap (red arrow). You can now remove the alternator from the engine. Installation of the new alternator is the reverse of removal.





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Comments and Suggestions:
Guest Comments: I've searched all over online with no success for how to do figure 5 release the clip on the wiring connection. Where do I insert a flat head screwdriver or other tool to release the clip from the alternator? The connector plug is stuck.
February 16, 2016
  Followup from the Pelican Staff: Look at figure 6. On the top of the connector on the alternator is the tab the connector locks onto. You will have to slide a flathead or small pick in from the alternator side to release the connector. That is the release button on the connector is not working. - Nick at Pelican Parts  

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