Wednesday, April 13, 2011

2003 Jetta GLX (V6) voltage issue problem?

A common problem has been an excessive voltage drop in the main charging system wire which causes the wire to overheat and melt the fuse box. The proper way to repair this is to replace both the battery auxiliary fuse box and the wire between the alternator and fuse box.

If this is what you have done and the alternator is still not charging, then we will need to run a few tests to see what is going on. Check for voltage at the alternator connector at the D+ terminal, with the harness unplugged from the alternator and the ignition in the on position (Blue wire), using a voltmeter. Approximately battery voltage should be present. If voltage is not to specification then test the wire using available wiring diagrams between the alternator and the Instrument Cluster (IC) . This circuit is the charging light circuit in the IC. When this wire is grounded the light should illuminate on the IC. Check for battery voltage on the B+ wire. Check for a good alternator case ground.
Perform a voltage drop test of the Black wire between the back of the alternator and the battery auxiliary fuse box. Replace the wire and fuse box if high voltage drop (more than 0.1 Volt) is found. Test the battery for load capacity. Use a jumper wire from the battery positive terminal to the D+ terminal and the alternator should start charging, if there is a good case ground. If the alternator will not charge it will need replacement.

Potential Causes:
Alternator Ground
Alternator Wiring
Battery Auxiliary Fuse Box
Instrument Cluster (IC)
First confirm this possibility.
the only wires that need to get power are the blue wire and the big positive wire going to the back of the alternator. Be sure ot check them both with the engine running.

The terminal of the alternator cable in my GLX V6 is impossible to get to without dropping the front end into a partial service position.
You would have to be very clever in order to do this. You would need to check for power to the back of the alternator with a long lead with a wire pierce ending on it. The only other way to do this would be with a scanner and try to run the charging output test. However, even then, if the alternator does not work when you do this, you still do not even know about the wiring going to the back of the alternator.

Check the voltage at alternator:----
voltage. 12.22V off. 11.99V idling. if it shows this, then its problem.
The exact voltage should be as follows:---
12.75 off and 14.30 on.
I knew the wiring is good because you just replaced the fuse panel box and alternator wiring harness/cable.
But this test can even pass if voltage regulator is not functioning.So check the voltage regulator.
the voltage regulator "inside" the alternator.-------------
order a new voltage regulator for about $60(US). drop the front end into the partial service position, pull the alternator, replaced the voltage regulator and then check the voltage.It should work.