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Pelican Technical Article:

Alternator Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$250

Talent:

**

Tools:

13 socket, 8mm wrench, pry bar

Applicable Models:

VW Golf GTI (2000)
VW Golf GTI 1.8T (2002-05)
VW Golf GTI 20th Anniversary (2003)
VW Golf GTI 337 (2002)
VW Golf GTI GLS (2001)

Parts Required:

New or rebuilt alternator

Hot Tip:

ALWAYS disconnect the battery before beginning

Performance Gain:

Car charges again

Complementary Modification:

Change V-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.

The first step in replacing any alternator is to disconnect the battery. 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. Please refer to our article on battery replacement for more info.

To remove the alternator you will first need to remove the V-belt, tensioner and the throttle body. Please see our articles on removing your V-belt, tensioner and throttle body, perform those jobs then come back here.

The alternator is mounted just to the side of the tensioner. There are two 13mm bolts holding it to the bracket. Remove these bolts.

There is going to be a very good chance you will need a pry bar to remove the alternator from its bracket. They tend to get corroded to the bracket over time and need a little help to release. Use caution as you do not want to damage the alternator or the bracket while doing this.

With the alternator free you need to remove a few things from the back before you can remove it from the engine compartment. Begin by disconnecting the electrical connection.

Remove the protective cap and the 13mm nut from the main electrical line.

Finally remove the 8mm nut holding the bracket that supports the wiring harness to the alternator.

You can now remove the alternator from the engine.

Installation is the reverse of removal.

The first step in replacing any alternator is to disconnect the battery.
Figure 1

The first step in replacing any alternator is to disconnect the battery. 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.

The alternator is mounted just to the side of the tensioner.
Figure 2

The alternator is mounted just to the side of the tensioner. You will first need to remove the V-belt, tensioner and the throttle body. Please see our articles on removing your V-belt, tensioner and throttle body, perform those jobs then come back here. There are two 13mm bolts (red arrows) holding it to the bracket. Remove these bolts.

There is going to be a very good chance you will need a pry bar to remove the alternator from its bracket (red arrow).
Figure 3

There is going to be a very good chance you will need a pry bar to remove the alternator from its bracket (red arrow). They tend to get corroded to the bracket over time and need a little help to release. Use caution as you do not want to damage the alternator or the bracket while doing this.

With the alternator free you need to remove a few things from the back before you can remove it from the engine compartment.
Figure 4

With the alternator free you need to remove a few things from the back before you can remove it from the engine compartment. Begin by disconnecting the electrical connection (red arrow).

Remove the protective cap and the 13mm nut (red arrow) from the main electrical line.
Figure 5

Remove the protective cap and the 13mm nut (red arrow) from the main electrical line.

Finally remove the 8mm nut holding the bracket that supports the wiring harness to the alternator (red arrow).
Figure 6

Finally remove the 8mm nut holding the bracket that supports the wiring harness to the alternator (red arrow).

You can now remove the alternator from the engine.
Figure 7

You can now remove the alternator from the engine. Alternator

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Page last updated: Wed 12/7/2016 02:34:58 AM