GLPoomobile 958 Posted October 1, 2007 (edited) Wasn't sure if I should put this here or in Misc Technical, but hey ho, here we go..... I was doing a bit of searching yesterday, and found a few bits of info that have either got me thinking, or just confused me 1 - If the alternator exciter wire is disconnected, will the alternator NOT charge the battery below 4000rpm? (according to Anthony, above 4000rpm the alternator self excites ) 2 - If the alternator exciter wire is disconnected, should the battery warning lamp in the dash be.. a - on fully when running b - on dimly when running c - always off, even with ignition switched on 3 - Should there be an earth connection to the starter? Mine has a thick permanent +VE on a ring terminal, which piggybacks to the alternator, and a spade connector with the blue starter solenoid wire that goes through the brown multiplug, but I've read posts referring to an earth from the starter to the gearbox Cheers Steve Edited October 1, 2007 by GLPoomobile Share this post Link to post Share on other sites
GLPoomobile 958 Posted October 1, 2007 Where's Graham/Rob/Jim when I need an answer? Share this post Link to post Share on other sites
flipperthebushkangaroo 2 Posted October 1, 2007 Wasn't sure if I should put this here or in Misc Technical, but hey ho, here we go..... I was doing a bit of searching yesterday, and found a few bits of info that have either got me thinking, or just confused me 1 - If the alternator exciter wire is disconnected, will the alternator NOT charge the battery below 4000rpm? (according to Anthony, above 4000rpm the alternator self excites ) 2 - If the alternator exciter wire is disconnected, should the battery warning lamp in the dash be.. a - on fully when running b - on dimly when running c - always off, even with ignition switched on 3 - Should there be an earth connection to the starter? Mine has a thick permanent +VE on a ring terminal, which piggybacks to the alternator, and a spade connector with the blue starter solenoid wire that goes through the brown multiplug, but I've read posts referring to an earth from the starter to the gearbox Cheers Steve hello had alternator woes myself a few weeks back so i know this was how mine worked 1 the alternator does not charge if the exciter wire is disconnected. 2. The battery warning light is fed via the exciter wiring so the light will be out. 3. just looking in the haynes manual will get back to you When my exciter wiring packed up the break was in the brown multi connector in the area under the oil fill point. Hope this is some help Roddie Share this post Link to post Share on other sites
flipperthebushkangaroo 2 Posted October 1, 2007 the motor itself is earthed via the case, one wire (smallish) goes t the solinoid and two larger wires go to the motor contactsone straight from the battery positive and one from the(to the?) alternator. if memory serves me right the one of the connectors can break down causing starting troubles. good luck Roddie Share this post Link to post Share on other sites
GLPoomobile 958 Posted October 1, 2007 Thanks Roddie, you've confirmed what I suspected. Well I reckon I've isolated at least one the sporadic faults I had with the car in the small mileage I covered in it. On 3 seperate occasions I found the car losing all electrics and therefore start stuttering really badly, lights dimming etc. I just put this down to a dodgy earth due to the catalogue of (what I perceive to be) bad wiring on my car. On all 3 occasions I solved the problem by revving the tits off of it until it cleared. Not a very well educated course of action, but it did the trick and now I know why. My excitation wire has sheared off of it's spade connector It looks like Anthony was correct when he said (in an old topic) that above 4000rpm the alternator self excites and charges the battery without relying on the excitation wire. I say this because in the mileage I covered I never once suspected a flat battery, presumably because I was enjoying my Mi as nature intended and spent plenty of time above 4k On all 3 occasions that I had the stuttering, I had been driving at lower revs for a fair while (stuck in traffic etc) and so the alternator was obviously not charging the battery. Once the battery got low on charge and the stuttering started to occur, I revved the nuts off of it and so the alternator started providing charge. Just as a matter of interest, does anyone know why I got a brief electrical burning smell on two of the occasions when I did this? I also had no battery warning light, but put this down to either a dead bulb or just a dodgy connection. Had I been a bit more educated on this side of things I would have checked the alternator sooner I also can't believe I never noticed the snapped wire considering it's not exactly hidden, but I'm not very observant. I'm glad I've found this out though, as I thought the problem was a dodgy earth, but my earth leads and connections look sound, so I was concerned that I would replace them and still have the fault. The other problem I had was no starter activity. I'm still pretty sure it's the brown plug but I suppose it could have just been low battery voltage due the above issue. I have a very large order to place with VWP and Simtek this week, and then hopefully I can get this lot sorted. God know's it's well overdue (I'm so slack I make students look busy ). Share this post Link to post Share on other sites
flipperthebushkangaroo 2 Posted October 1, 2007 No problem, ref the burning smell does the voltage regulator look ok, depending on the type it is the plastic bit on the end (cracking technical description!!) i've had them go as well. Anyway best of luck with it. Share this post Link to post Share on other sites
jonnie205 1 Posted October 1, 2007 alt will charge battery with exciter wire disconnected battery light on dash will never illuminate with wire disconnected no earth lead required from alt to block, earth lead only needed on rubber mounted alternators Share this post Link to post Share on other sites
