Replacing an alternator in a Volkswagen Jetta is necessary if inspection of the charging system reveals it is faulty. The Jetta’s charging system includes the alternator, voltage regulator, a charge indicator, fusible link, the battery and the wiring connecting all the components. Under normal conditions the dashboard warning light will come on when the ignition key is turned to start, and should go off immediately. If the light stays on there is a malfunction in the system. If the alternator is the culprit, most home mechanics have the tools and expertise to change the VW’s alternator and save a substantial amount of money in the process.
- Skill level:
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Things you need
- Socket wrench
- Socket of appropriate size for model year
- Adjustable wrench
- Pry bar
Detach the cable from the negative terminal post on the battery to prevent painful shock or damage to the new part or other electrical components in the Jetta.
Remove the electrical connectors from the old alternator. Disconnect every wire to ensure easy removal.
Loosen the pivot and adjustment bolts. Back them off two or three turns to release tension on the drive belt. Some later model Jettas have a tensioner built into the adjuster assembly; if present, use a wrench to loosen the toothed adjusting bolt.
Remove the drive belt. Inspect the belt for signs of wear. Replace the drive belt if wear is apparent when installing the new alternator.
Remove the adjustment and pivot bolts. Retain the bolts for installation of the new alternator.
Detach the alternator from the Jetta's engine. Save the part and return it to the parts store for core credit.
Seat the new alternator in the same position as the old one.
Tighten the pivot and adjustment bolts. Do not tighten completely.
Attach the wires. Connect the wires the same way as on the old alternator.
Install the drive belt. Follow the same path the belt previously occupied.
Tighten the adjustment and pivot bolts. Adjust the drive belt so it is snug but not tight. Some later model Jettas have a tensioner built into the adjuster assembly. If present, use a wrench to tighten the toothed adjusting bolt.
Reattach the negative battery wire. Start the vehicle and observe operation of the drive belt. It should move smoothly and freely on the pulleys.
Test the new alternator’s output. Use the voltmeter to determine the replacement part is functioning properly before driving the Jetta.
Tips and warnings
- Have a year-appropriate auto repair manual on hand before you begin. The pictures and advice are invaluable to the do-it-yourselfer.
- When you remove the electrical wires from the alternator, label them accordingly to ensure proper reinstallation.
- Using a pry bar to coax the alternator into proper position for tightening the drive belt turns a two-person job into a one-person operation.
- Replacement alternators, especially refurbished ones, are not always 100 per cent. Check the voltage output before you take off or you may be stranded.
- Never work on a vehicle’s electrical system until after disconnecting the negative battery cable. Serious harm could occur.
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