dave123456789 Posted July 16, 2010 Share Posted July 16, 2010 Hey guys I have been trying to work out why my battery doesnt charge. It charges at 13.5V with no lights etc on but as soon as I turn my lights on it dips to 11.8-12.3 if I rev the shit out of it. 3.3L vauxhaul motor Quote Link to comment Share on other sites More sharing options...
R100 Posted July 16, 2010 Share Posted July 16, 2010 Could be volt drop between the positive on the alt and battery. or voltdrop between alternator caseing and battery. Chuck your voltmeter accoross thos 2 points to check. Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted July 16, 2010 Author Share Posted July 16, 2010 I chucked the meter on the positive on the alt and earthed the other end and its giving pretty much the same readings, all way too low to charge the battery. Also that 13.5V with nothing on is more like 12.7-8 at idle and low 13s with revs. I guess this means my alt is stuffed? Quote Link to comment Share on other sites More sharing options...
R100 Posted July 16, 2010 Share Posted July 16, 2010 To do a volt drop test put one end of the voltmeter onto the alternator caseing and the other to the negitive on the battery. Should read a maximum of .2 volts then put one end of the voltmeter on the positive terminal on the alternator and the other end to the positive on the battery, again should read no more than .2 of a volt Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted July 16, 2010 Author Share Posted July 16, 2010 To do a volt drop test put one end of the voltmeter onto the alternator caseing and the other to the negitive on the battery. Should read a maximum of .2 volts then put one end of the voltmeter on the positive terminal on the alternator and the other end to the positive on the battery, again should read no more than .2 of a volt Ok with the meter on the alternator case and negitive battery i get pretty much nothing, highest was 0.01. with the meter on the alternator positive and the positive on the battery i got 0.08 Quote Link to comment Share on other sites More sharing options...
R100 Posted July 16, 2010 Share Posted July 16, 2010 Ok thats a good reading. Is it internally or externally regulated ? And i assume your warning light on the dash goes out ? If it does go out is it glowing very faintly. You will need to look at it in the dark to see this. Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted July 16, 2010 Author Share Posted July 16, 2010 Ok thats a good reading. Is it internally or externally regulated ? And i assume your warning light on the dash goes out ? If it does go out is it glowing very faintly. You will need to look at it in the dark to see this. Its externally regulated, the warning GEN light goes out and is completely out. Just checked it in a pitch black garage. Thanks for you help so far, been pissing around with this all night browsing google on the laptop trying to get it sorted before I have to pay someone to do it. Quote Link to comment Share on other sites More sharing options...
R100 Posted July 16, 2010 Share Posted July 16, 2010 A couple more questions befor i head off to bed. If its externally regulated is the regulator to big old plastic type or it is the size of a matcbox ? Your proplem is going to be one of 2 things. One of the diodes on the rectifier has blown. This will most likely be visible if you pull the alternator apart. When a diode blows the warning light will still go out and voltage will increase slightly but not enough to charge the battery. If its the old type large plastic regulator then chances are that could be the problem, but the fact the warning light goes out tells me its more likely a faulty rectifier. Long story short. Replace the alternator. Its not economically viable to repair such an old style of alternator. Better still, adapt a internally regulated jap style alternator, easy peasy to wire up and generally wont cause any problems. Pull your alternator apart for peice of mind, see if any of the diodes have shit themselves. Get a screw driver to gently tweak each diode and the shit one will usually just pry apart. Of coarse all of what i say is just based on what you have told me. Quote Link to comment Share on other sites More sharing options...
dave123456789 Posted July 16, 2010 Author Share Posted July 16, 2010 A couple more questions befor i head off to bed.If its externally regulated is the regulator to big old plastic type or it is the size of a matcbox ? Your proplem is going to be one of 2 things. One of the diodes on the rectifier has blown. This will most likely be visible if you pull the alternator apart. When a diode blows the warning light will still go out and voltage will increase slightly but not enough to charge the battery. If its the old type large plastic regulator then chances are that could be the problem, but the fact the warning light goes out tells me its more likely a faulty rectifier. Long story short. Replace the alternator. Its not economically viable to repair such an old style of alternator. Better still, adapt a internally regulated jap style alternator, easy peasy to wire up and generally wont cause any problems. Pull your alternator apart for peice of mind, see if any of the diodes have shit themselves. Get a screw driver to gently tweak each diode and the shit one will usually just pry apart. Of coarse all of what i say is just based on what you have told me. The regulator is a big box about the size of a packet of cigs. Ok i will take my alternator off and check those things that you mentioned. If it is truely stuffed i'll hunt around for something that will either fit in its place or i'll have to make up some new brackets. Gutted was hoping that this would be a nice easy fix. Thanks for your time Quote Link to comment Share on other sites More sharing options...
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