Kitch 4 Posted January 20, 2007 The charging circuit? Odd question I know, but I recently chipped my car and now it doesn't charge properly. The alternator can't be two years old and the car has done about 8000miles in this time! Any ideas? Cheers Share this post Link to post Share on other sites
Faz85 0 Posted January 20, 2007 I dont think its possible, have you checked the usual just to be sure? get a voltmeter on the alternator to check charge voltage, and checked the earths etc... Im not sure but I guess there is a slight possibility that something in the ECU is shorting to earth. Share this post Link to post Share on other sites
jackherer 543 Posted January 20, 2007 No the ECU is unconnected to charging the battery. The wiring between the alternator and the dashboard for the battery light can affect charging though, without a good connection here the alternator wont work. I assume you're talking about your BX 16v? If so the wiring for the bat light goes from the alternator to a white multiplug (IIRC) that is similar to the infamous 205 brown multiplug, and after this it goes through the bulkhead on the passenger side. The most likely place for a problem with this wire is the connection to the alt itself. Is your battery light coming on? How old is the battery itself? Share this post Link to post Share on other sites
Kitch 4 Posted January 20, 2007 YES! You're right, the battery symbol on the dashboard is missing! The battery itself doesn't look old, but can't be sure. Its a big unit too, more of a diesel one. I did test the alternators output, the first reading was 13v, the second was 5v about 10mins later and another 10mins later it was pushing out 8v....work that out Am I right in thinking that the alternator knows how much to charge by reading what the battery has, and if the earth in that symbol's wiring was out then the alternator wouldn't know what to charge? You're quite correct, it is the BX 16v. So how do I get this lamp to come back? Share this post Link to post Share on other sites
jackherer 543 Posted January 20, 2007 Is the small spade connector firmly connected to the alternator? No corrosion here? If thats OK then check the multiplug, and if that seems OK it might be the bulb itself has blown. Share this post Link to post Share on other sites
Kitch 4 Posted January 20, 2007 So if the bulb has blown, that can affect the alternator's output? Share this post Link to post Share on other sites
dee205 3 Posted January 20, 2007 If the light only comes on when the alternator isn't getting a charge this would suggest no power going through the buld when charging. So a blown bulb wouldn't affect it. Damien Share this post Link to post Share on other sites
jackherer 543 Posted January 20, 2007 TBH I'm not sure, if there is a break in the wiring that will definitely affect it but I don't know for sure about the bulb itself. Share this post Link to post Share on other sites
Faz85 0 Posted January 20, 2007 The battery itself doesn't look old, but can't be sure. Its a big unit too, more of a diesel one. I did test the alternators output, the first reading was 13v, the second was 5v about 10mins later and another 10mins later it was pushing out 8v....work that out I was under the impression that the voltage accross the terminals should be about 14ish volts and thats always, regardless of the demand on the battery. surely if there is a break in the wiring, the alternator wouldnt charge at all would it? I reckon it could be the alternator itself, changing it for a known good-un would at least eliminate the possibility. Share this post Link to post Share on other sites
crogthomas 0 Posted January 20, 2007 Older alternators needed current to pass through the dash light to excite the field windings before the alternator could begin outputing charge. Once the alternator is producing charge it provides current to the field windings itself and the dash light then extinguishes. Not sure how relevant this is to the type of alternator fitted to your car, but yes, it is possible that a blown dash light could prevent the alternator chargeing. Share this post Link to post Share on other sites
Anthony 1,003 Posted January 21, 2007 The alternator will usually charge even with that spade connector disconnected, but normally you'll need to give it 3000-4000rpm before it'll start charging. Easy enough to test the bulb and wiring though - just unplug the spade connector and short it against the block - the light should come on. Just had an alternator fail on the 205 van that I'm borrowing at the moment, and when that gave up the ghost the dash light didn't come on when you switched the ignition on - no charge at all from it Share this post Link to post Share on other sites
