Scammell4199 Posted May 16, 2009 Share Posted May 16, 2009 My Jeep appears to be not charging. With the engine running, if I turn the lights on the Ammeter flicks into the negative side, so I presume that means the ammeter is working, but when I rev the engine, the ammeter is motionless. Under instruction from Tony Sudds I disconnected the two large terminals from the generator and bridged them, then with the engine running put a meter accross the bridged terminals and the negative terminal on the battery, this was supposed to produce 14 - 15 volts but I only got 0.30!! Can I presume from this that the generator needs looking at? The regulator is a 12 volt unit from a Mini mounted inside the original casing. Can the generator be tested further by connecting it up to run like a motor? I'm going to check the brushes in the generator, but any help will be greatfully recieved - shes got to be sorted in time for the Normandy trip. Thanks in advance, Richard Quote Link to comment Share on other sites More sharing options...
Scammell4199 Posted May 17, 2009 Author Share Posted May 17, 2009 Further to the above after doing a bit of reading on the subject, is it necessary to polarize the generator and how would I do this? Richard Quote Link to comment Share on other sites More sharing options...
Swill1952xs Posted May 17, 2009 Share Posted May 17, 2009 My Jeep appears to be not charging.With the engine running, if I turn the lights on the Ammeter flicks into the negative side, so I presume that means the ammeter is working, but when I rev the engine, the ammeter is motionless. Under instruction from Tony Sudds I disconnected the two large terminals from the generator and bridged them, then with the engine running put a meter accross the bridged terminals and the negative terminal on the battery, this was supposed to produce 14 - 15 volts but I only got 0.30!! Can I presume from this that the generator needs looking at? The regulator is a 12 volt unit from a Mini mounted inside the original casing. Can the generator be tested further by connecting it up to run like a motor? I'm going to check the brushes in the generator, but any help will be greatfully recieved - shes got to be sorted in time for the Normandy trip. Thanks in advance, Richard If you are testing the dynamo output, disconnect the wiring to the dynamo and bridge the terminals as you said. Put a voltmeter between the bridged terminals and the EARTH connection on the battery. If it is a twelve volt generator then at about 1/4 to half throttle, you should get about 30v from it. That is the only test you will need to do to confirm that the dynamo is working. As regards polarising the dynamo......... disconnect the wiring to it. Connect a wire to the LIVE side of the battery and flick it across the smaller terminal on the dynamo, several times. This will cancel any residual magnetism in the field coils and re- polarise it for your earthing sysytem. If it still fails to charge, then check that the dynamo is earthed to the engine, check the wiring to the regulator. I assume your electrics have been converted to 12v if you are using a Mini regulator. If the dynamo test and wiring check are all ok, then it's most likely a regulator fault. Regulator contacts can corrode when not in use and may need cleaning. (Contact points inside the unit) Jus' tryin ta be helpful........ Will Quote Link to comment Share on other sites More sharing options...
Tony B Posted May 17, 2009 Share Posted May 17, 2009 Swill's right, it does sound like a depolarised genarator. A forgotten bit of lore that! A lot of people caught out by it! Quote Link to comment Share on other sites More sharing options...
Scammell4199 Posted May 17, 2009 Author Share Posted May 17, 2009 Thanks very much for that guys. Just to go over the polarising thing a bit, the vehicle has been running fine since I finished rebuilding it in 2004, and I never polarized it then, so does this mean the generator has just become de-polarized sometime recently, how could this have happened? Swill, to go over the technique for this you say to disconnect all the wiring and strike the small terminal with a wire from the positive terminal on the battery, the small terminal is the earth on a Jeep, also if you've disconnected all the wiring, and strike it with one wire from the battery theres no circuit is there? Not questioning, just want to fully understand whats going on. Many thanks, Richard Quote Link to comment Share on other sites More sharing options...
Tony B Posted May 17, 2009 Share Posted May 17, 2009 IMPORTANT!!!!!!!!!! Make sure you take the reghulator out of cicuit before you do it. I've known it blow the regulator. Better safe than sorry! Quote Link to comment Share on other sites More sharing options...
Swill1952xs Posted May 17, 2009 Share Posted May 17, 2009 Thanks very much for that guys.Just to go over the polarising thing a bit, the vehicle has been running fine since I finished rebuilding it in 2004, and I never polarized it then, so does this mean the generator has just become de-polarized sometime recently, how could this have happened? Swill, to go over the technique for this you say to disconnect all the wiring and strike the small terminal with a wire from the positive terminal on the battery, the small terminal is the earth on a Jeep, also if you've disconnected all the wiring, and strike it with one wire from the battery theres no circuit is there? Not questioning, just want to fully understand whats going on. Many thanks, Richard If the dynamo is earthed to the engine, there should be a circuit as the field coils must be earthed to the engine. The field coils determine the amount of magnetism acting on the armature, and consequently the charging output. This is controlled by the regulator. Hopefully this information is correct as I haven't had dealings with dynamo's for some years now. Maybe someone could verify the information. Quote Link to comment Share on other sites More sharing options...
Scammell4199 Posted May 19, 2009 Author Share Posted May 19, 2009 Thankyou all very much for your help, its helped me understand whats going on in the charging system a bit better. I took the generator off at the weekend and father took it to the rewind centre in Yeovil yesterday, and a phone call a short while later revealed that corrosion on the inside of the yoke had make contact with the field windings breaking through the varnish insulation and shorting it out. Thanks again, Richard Quote Link to comment Share on other sites More sharing options...
Tony B Posted May 19, 2009 Share Posted May 19, 2009 Will DEFINITLEY need re-polarisng on refit then! Get them to write the procedure for you. The instructions always used to come in the box. Quote Link to comment Share on other sites More sharing options...
89sbr Posted May 22, 2009 Share Posted May 22, 2009 I picked up this thread as I am also having problems with my MB. I followed the above procedures and worked out that the dynamo was kaput. I managed to get a dynamo which worked and I fitted it to my jeep. I bridged the field and amm connections and measured 30volts. Great but my ammeter (New One) showed a discharge when under load but no charge. I use an American regulator I don't know the make and it looks fairly new. I checked the battery tab and there is a feed there but the other 2 tabs the amm and the field both have negative feeds and when the motor is running there is sometimes a very slight voltage and then nothing. I assume the regulator is also not working as it should and I wonder if a mini one would be OK. The dynamo is a Lucas item. Hope you can help I go to Normandy in 12 days and counting. Steve Quote Link to comment Share on other sites More sharing options...
Scammell4199 Posted May 25, 2009 Author Share Posted May 25, 2009 I know I said my reg was a mini one but its not it was actually a new one when I installed it in 2004, its from Lucas and its a model RB340 - standard no frills 12v reg as I understand. As far as my simple understanding on the subject goes, you won't be able to measure the field and amm connections on a reg because they are connected to the voltage and current solenoids which are opening and closing 50 - 200 times a second. For a bit of basic learning on the subject check out: http://www.secondchancegarage.com/public/91.cfm and follow on to part 3 at the bottom of the page. Sounds to me as though your reg has had it. Try calling Tony Sudds and see what he says: 01474703131 Let us know how you get on. Richard Fryer Quote Link to comment Share on other sites More sharing options...
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