45 My charge light does not behave as expected. What is wrong?
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This article is from the VW Technical FAQ, by with numerous contributions by Jan Vandenbrande others.
45 My charge light does not behave as expected. What is wrong?
A: Taken from EC (March 1994):
The charges light is directly connected to the excitor part of the
alternator. It provides the initial power to get the alt working.
And it also provides alot of additional info:
Engine off, ignition on, no charge indicator:
- Lamp burned out, wiring break, internal alt failure, voltage regulator
bad. Alt will NOT charge!
- [From Jens]: Broken rotor wire.
The alternator brushes may be bad which means too short, they should
be at least 5mm out of their housing. If the brushes are wet or
dirty cleaning can help, if not, you have got to change:
o Bosch alternator: change only the brushes.
o Valeo alternator: you must change the complete regulator :-(
o Motorola alternator: the brush carrier has to be changed
Engine running, charge indicator on:
- Alt is not charging. Belt loose, bad voltage regulator.
- [From Jens]: Exciter diodes broken
Charge indicator on, engine & ignition off:
- At least one of the 3 diode groups is shorted. Alt is only partially
charging. Have it serviced/replace diodes.
- [From Jens]: Plus diodes are shorted.
Charge indicator out at idle, half intensity at higher rpms:
- At least one of the 3 diode groups is open. Alt is only partially
chanrging. Have it serviced/replace diodes.
- [From Jens]: Bad brushes, see above.
Charge indicator glows dimly under electrical load (most noticable at night):
- Bad connection between alt and battery (see above).
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