Leece Deville alternator

With only one post I can’t tell your abilities on testing??? Are you saying when you turn the key on there isn’t 12V at the alternator or the alternator does not work???

MrWizard wrote:
... excitation of the alternator field winding come from the voltage regular and / or the engine CPU

Depends on the "vintage" of the charging system !

On older charging systems, the field was "excited" through the key and the "idiot" light. If there idiot light had failed, the alternator would not get excited when you started the engine. It may or may not "self excite" after the engine was running.

If this is a DUVAC alternator, these are the connections:

B+ to battery isolator (large-gauge wire)

Ground-- may be separate wire or may ground through engine (metal to metal)

Ignition hot small terminal/excite terminal-- gets power from any ignition hot connection in engine compartment

Sense small terminal-- small gauge wire connected anywhere on the "battery side of the battery isolator".


The last two are small gauge wires and can break. Pretty easy to check with a digital voltmeter.

Do you mean the alternator is not charging the battery

Power flow is from battery Too ignition
And from alternator to battery


excitation of the alternator field winding come from the voltage regular and / or the engine CPU