Question about 1987 Toyota Land Cruiser

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Not charging at low idle

When the engine is at low idle, the alternator is not keeping up

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Some times when the alternator brushes is short can be,.so check alternatoe brushes.

Posted on Nov 07, 2008

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How have you determined "not keeping up"?

We need to diagnose whether the culprit is the alternator or battery (or something else like an accessory drawing more than normal current)

With a digital voltmeter (not analog) , measure battery with car off, then compare battery at idle.
Off reading = about 12.6 - 12.8 volts DC
Idle reading must be higher than above or no charging will take place, Idle volts typically 13 - 13.5 and should increase a bit with RPM until regulator limits the increase.

Some possibilities are :

  1. bad diode in alternator (can be replaced separately in many alternators)
  2. bad regulator (built-in to modern alternators)
  3. bad connection at battery terminals (wire brush or use battery terminal cleaning tool)
  4. bad battery (shorted cell, often caused by allowing water level to go below tops of lead plates)

Posted on Oct 25, 2008

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