suggs Posted November 23, 2007 Share Posted November 23, 2007 am i correct in that if im getting about 12.9-13v at the battery with the engine running, and if i disconect the alternator and the volts drop to 12v at the battery then everything is charging correctly? as ive just had a flat battery and its only a few weeks old, shortly after fitting a new battery the alternator belt snapped and battery whent flat driving home, after i replaced the belt i jump started the 90 and drove about 20 miles, since then ive only done a quick local trip when it started but didnt fell like it had a full punch to it. its since been parked up for a week in the cold weather and today it was flat as a pancake. it jumped started straight up and then i used a multi meter to get the above results, im just trying to find out if its the alternator, battery or if it just wasnt fully charged and the cold has knocked it out. ive now got it on charge.. cheers Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted November 23, 2007 Share Posted November 23, 2007 if i disconect the alternator and That's a bad thing to do, alternators don't like being ran without a battery on them. A charging battery should have ~14.4 across it. above that it'll gas. 13.9 upwards is in the right ball park. an alternator won't be charging properly until ~2k rpm. A battery at rest should show 12.5 ish. Once a battery's been below 10v it will cause damage, it's possible to 'repair' some of this by checking the acid level and then leaving the battery on a trickle/maintainance charger. It will probably never regain 100% performance though. Battery post here Quote Link to comment Share on other sites More sharing options...
sgnas Posted November 23, 2007 Share Posted November 23, 2007 With the engine running, at more than tickover, I would expect ~14.5volts on the battery. Could be that the alternator isn't putting out the right voltage or It was still trying to pick up an under voltage battery Measure it again with the battery charged and with the engine revs up a bit. Quote Link to comment Share on other sites More sharing options...
suggs Posted November 23, 2007 Author Share Posted November 23, 2007 cheers i just pulled the conection of the alternator for a minuit to see if there was any diffarence, as above there was about 1 volt more with it connected but still only about 13v at tickover, i had no problem before the belt snapped although i did get stuck in some serious deep mud, hence a stone got in the pulley and thats what snapped the belt. hope i didnt kill the alternator!! Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted November 23, 2007 Share Posted November 23, 2007 Keep running it unloaded and you will. Quote Link to comment Share on other sites More sharing options...
suggs Posted November 23, 2007 Author Share Posted November 23, 2007 seems to be rising now its been on charge for a few hours, getting 13.7+ at tickover.. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted November 23, 2007 Share Posted November 23, 2007 Brushes could be gunged up, squirt the hose through it for a bit then douse with WD40 (try to get it inside esp. the back) to dry it out. They don't mind clean water, but mud will clog them up. Have had to unstick the brushes on dad's alt quite a few times. Quote Link to comment Share on other sites More sharing options...
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