I have a 2003 Jetta Station Wagon with a 1.8T 5spd. When the car is idling and while I'm driving the dashlights and headlights pulsate. The car also idles up and down a bit and the fuel pump makes a whirring noise. I've replaced the fuel filter, spark plugs, and the alternator. Any help is greatly appreciated.
My car has 224000 miles.
My car has a manual transmission.
The battery and charging system is most likely the malfunction. If the battery is shorting out internally it would cause the alternator to not charge. There is a technical bulletin about not using re-manufactured alternators on these cars since they had problems of not charging properly. You should have your vehicle system checked by a mechanic like one from YourMechanic to see if the battery and cables are good and if the alternator is charging properly.
I have seen this quite a few times on this vehicle. It is almost always caused by loose or dirty ground connections. I typically remove the ground connections on the negative cable first and clean them and make sure they are tight. If those are fine I then check the grounds connected to the engine. Some of the time it can be a bad connection at the module, but most of the time it is the grounds. If you are going to have this repaired, consider YourMechanic, to have a certified mechanic come to your home or office to https://www.yourmechanic.com/services/service-battery-cables.
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