hi all never posted on this forum but havin a problem with my 2004 2.8crd alternator
the other day came to start car wasnt enough power in battery to start so put battery charger on and then started ok set off went about 5 mile then i broke down battery flatt again got it home and put multi meter on battery with engine started and was only getting 11.6v even if i reved it which then kept dropping slowly i have checked the pulley and the alternator is spinning inside ok now before i buy a new alternator which i have been told is £314, been told the voltage regulator is in the power control module and it could be that i have put my tester straight to the main connection on the back of the alternator and still only 11.6v when engine running, from what i have read the alternator will give out about 18v and then the pcm voltage regulator will reduce it to whatever it needs so in theory i would presume that i should still be getting 18v at the alternator where the big wire bolts on even if it was the pcm voltage regulator wasnt working or am i miss understanding how it works lol and if so is there any tests i can do to find out what is causing the problem cheers

 

OK have you checked the pulley properly? it may be turning but not fast enough. You need to remove the belt and turn the pulley by hand. If you then lock up the alternator (carefully) but a small screw driver in the front of the alternator to contact the fan blades, then turn the pulley by hand. It should only turn one way if you can turn both ways the pulley is faulty.
The voltage at the alternator should always be what you have at the battery.

 

hi merlin thanks for the reply the pulley is definatley spinning the same speed as the engine, what i was trying to say in my first post was if the voltage regulator in the pcm fails would the alternator still give out 18v to the voltage regulator but obviously then cant charge the battery because regulator was shot or does the regulator in the pcm send some sort of signal back to the alternator to make it start charging if that makes any sense

 

Hi
you have 2 wires on the alternator to control the field windings this is how the ECM controls the output from the alternator.