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Pelican Technical Article:

Alternator Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$200 to $600

Talent:

**

Tools:

13mm socket, 17mm, 10mm, 8mm wrench, pry bar

Applicable Models:

VW GTI (2006-09)

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 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 amply 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 engine running at idle, turn on headlights and HVAC blower motor. Never disconnect a battery cable while engine is running to test alternator, you may cause damage to 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 the alternator will need to be replaced.

You will need to remove the drive or ribbed belt and the charged air pipe to perform this work. Please see our article on removing your drive belt and charged air pipe for assistance.

Disconnect the ground strap from the battery terminal (red arrow) and place the cable (yellow arrow) where it can not accidentally come in contact with the battery while working.
Figure 1

Disconnect the ground strap from the battery terminal (red arrow) and place the cable (yellow arrow) where it can not accidentally come in contact with the battery while working. You will be working around live electric wires here. 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.

The charged air pipe and hoses run from the induction system and divert air before it reaches the throttle body (red arrow).
Figure 2

The charged air pipe and hoses run from the induction system and divert air before it reaches the throttle body (red arrow). This charged air runs through a pipe that is secured by an 8mm bolt (blue arrow) and T30 Torx (green arrow) and enters the interior by a quick release fitting (yellow arrow). Please see our article for removal procedures.

Remove the ribbed drive belt and lock the tensioner in the locked position.
Figure 3

Remove the ribbed drive belt and lock the tensioner in the locked position. Begin by marking the direction of the belt (red arrow), place a 17mm wrench (yellow arrow) on the nub on the tensioner and turn it clockwise, then insert a 3mm Allen to lock (green arrow) in position. Please see our article on replacing your ribbed drive belt for additional assistance.

begin by removing the dip stick (red arrow) to give you more room and to prevent breakage.
Figure 4

begin by removing the dip stick (red arrow) to give you more room and to prevent breakage. Next, remove the two 10mm fasteners (yellow arrows) holding the water line brackets. You do NOT need to remove the water lines, just the brackets.

Disconnect the connection for the DF wire (red arrow).
Figure 5

Disconnect the connection for the DF wire (red arrow).

Remove the cap on the B+ wire, and then the 13mm nut.
Figure 6

Remove the cap on the B+ wire, and then the 13mm nut. Remove the wire from the alternator.

Next, remove the two 13mm bolts holding the alternator to the bracket (red arrows).
Figure 7

Next, remove the two 13mm bolts holding the alternator to the bracket (red arrows).

Use a pry bar and gently wiggle and pry the alternator from the mount (red arrow).
Figure 8

Use a pry bar and gently wiggle and pry the alternator from the mount (red arrow). Note; use caution not to damage the wiring inside the alternator.

There is an 8mm nut holding the wiring harness in the back of the alternator.
Figure 9

There is an 8mm nut holding the wiring harness in the back of the alternator. Once the alternator is free of its mount you can get a better angle on removing the wiring harness bracket (red arrow).

With everything disconnected you can remove the alternator from the vehicle.
Figure 10

With everything disconnected you can remove the alternator from the vehicle. There is very little room to work but it will come out. I removed the belt tensions three 13mm bolts and removed the tensioner to make more room. Installation is the reverse of removal.

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Comments and Suggestions:
Jay Comments: Removing the belt tensioner makes it 10x easier to get the alternator out. It only takes an additional 5 min. to do and gives you plenty more space to work.
April 8, 2015
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 

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