daverclasper Posted August 20, 2019 Report Share Posted August 20, 2019 Hi. I have hopefully diagnosed this as the dynamo, as with a connecting wire between the 2 dynamo terminals give rapidly fluctuating readings of between 4 and 6 volts. Apparently these readings point to the armature being damaged, maybe by the control box cut out contacts not opening and battery charge going into the armature. My ignition light is on at rest and with the engine idling, so maybe I can assume the cut out is currently working?, before I replace the dynamo. Anything else I should look out for in control box?. Thanks, Dave Link to comment Share on other sites More sharing options...
johny Posted August 20, 2019 Report Share Posted August 20, 2019 yes Dave that should indicate a dynamo problem, most likely worn brushes and/or commutator. Unlikely to be armature or field windings as you'd smell it so remove back cover for a looksee.... Link to comment Share on other sites More sharing options...
daverclasper Posted August 20, 2019 Author Report Share Posted August 20, 2019 Thanks Johny. It has the charging issue, since I bought the car five years ago (disgraceful Iv'e only just got around to it, I know!), so maybe no burnt smell anymore?. Dave Link to comment Share on other sites More sharing options...
johny Posted August 20, 2019 Report Share Posted August 20, 2019 Normally what happens is the brushes wear down and start to make poor contact with the commutator so theres still some power produced but its not very stable. This worsens over time and normally results in burning of the commutator (beyond repair?) and no charging..... The field coil can easily be tested for continuity resistance to earth (5.9 +/- 0.3 ohms) while the armature has to be tested across each pair of commutator segments (all should have the same resistance). Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 20, 2019 Report Share Posted August 20, 2019 Just never mess with the control box small adjustments can make for disaster charging rates Pete Link to comment Share on other sites More sharing options...
SpitFire6 Posted August 20, 2019 Report Share Posted August 20, 2019 Hi, Just posted on the Slooow Forum: Hi, I would dump the electromechanical 60's Control box innards and replace with a solid-state module. The prebuilt ones are not cheap but better in every way! Cheers, Iain Link to comment Share on other sites More sharing options...
daverclasper Posted August 20, 2019 Author Report Share Posted August 20, 2019 Thanks folks. I have an apparently recon dynamo, that I picked up for a cheapish price. Will fit that and see how it goes. If ok, then dismantle the old one to see what's, what. If there is an ignition light on at engine rest and idle, does that infer the cut out contacts are not staying closed and therefore working at some level?. Dave Link to comment Share on other sites More sharing options...
johny Posted August 20, 2019 Report Share Posted August 20, 2019 the ign light on means the voltage out of the dynamo is less than the battery voltage and the cut out contact will be open to stop a reverse flow of current. Link to comment Share on other sites More sharing options...
poppyman Posted August 20, 2019 Report Share Posted August 20, 2019 If you connect the dynamo to a battery just with bits of cable it should run like a starter motor but very slowly.... If it runs? it's ok if not? it is kapput. Tony. 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted August 20, 2019 Report Share Posted August 20, 2019 24 minutes ago, poppyman said: If you connect the dynamo to a battery just with bits of cable it should run like a starter motor but very slowly.... If it runs? it's ok if not? it is kapput. Tony. With the field connected as well or it go kapuff 1 Link to comment Share on other sites More sharing options...
johny Posted August 21, 2019 Report Share Posted August 21, 2019 10 hours ago, poppyman said: If you connect the dynamo to a battery just with bits of cable it should run like a starter motor but very slowly.... If it runs? it's ok if not? it is kapput. Tony. I prefer the WSM test using a voltmeter to measure the dynamo output with the engine running to prove its working.... Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 21, 2019 Report Share Posted August 21, 2019 Care if motoring you dont reverse the polarity In the end of the day ditch it all and fit a period alternator, far more reliable and more consistent output Pete 2 Link to comment Share on other sites More sharing options...
TomL Posted August 21, 2019 Report Share Posted August 21, 2019 If you decide to go down the replacement-route and want to keep the appearance of a dynamo, you could try a dynamato, such as this: https://www.ebay.co.uk/itm/For-Triumph-Dynamator-Alternator-conversion-replaces-Lucas-C39-40-Dynamo/391929751620?fits=Model%3AVitesse&hash=item5b40d56844:g:XOUAAOSwpvZaEE6w Tom Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 21, 2019 Report Share Posted August 21, 2019 at more than 2 times the price its a serious decision a simple A127 as fitted by triumph in later years is still in the family makes an economical swap https://www.ebay.co.uk/itm/NEW-ALTERNATOR-12V-A127-RH-70AMP-LRA00460-FOR-FORD-JCB-TRIUMPH-MASSEY-AUSTIN/293123813468?hash=item443f8a705c:g:p3UAAOSweEJc7pl6 Link to comment Share on other sites More sharing options...
johny Posted August 21, 2019 Report Share Posted August 21, 2019 Certainly trumps the 25A output of the original dynamo.... Link to comment Share on other sites More sharing options...
daverclasper Posted August 21, 2019 Author Report Share Posted August 21, 2019 9 hours ago, Pete Lewis said: Care if motoring you dont reverse the polarity Hi Pete. Is that motoring, or monitoring?. Link to comment Share on other sites More sharing options...
johny Posted August 21, 2019 Report Share Posted August 21, 2019 no, definitely no typo there, its motoring.... Link to comment Share on other sites More sharing options...
daverclasper Posted August 21, 2019 Author Report Share Posted August 21, 2019 Can you explain that please, as Iv'e no idea. Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 21, 2019 Report Share Posted August 21, 2019 Its when you apply a battery feed to the dynamo it will make it rotate as a motor...hence motoring Pete Link to comment Share on other sites More sharing options...
SpitFire6 Posted August 21, 2019 Report Share Posted August 21, 2019 Hi, An A127 is as good replacement alternator up to around 80A on a single pulley I believe. Make sure its machine sensed. i.e. the two B+ terminals are shorted internally or externally together. The alternator to battery feed cable will work but a parallel cable will allow more loads to be added without visible volt drops. Cheers, Iain. 1 Link to comment Share on other sites More sharing options...
daverclasper Posted September 16, 2019 Author Report Share Posted September 16, 2019 (edited) Hi. Have fitted the recon dynamo. The voltage, direct from dynamo, is reading similar to the old one. It looks like it has been reconditioned, in that it all looks very clean/new through the back cover, the bearing felt looks new, I think I can see the brushes extending about 10mm from the top of the carriers. The 2 screw heads are a bit mullered, though maybe they use the old ones?. The field coil resistance is 6.3, measured with dynamo fitted. Is this a tad too high to make much difference?. Could I be doing something wrong, when measuring the voltage?. Thanks, Dave Edited September 16, 2019 by daverclasper Link to comment Share on other sites More sharing options...
Gary Flinn Posted September 17, 2019 Report Share Posted September 17, 2019 I'm having similar charging issues with my car, I found this link very helpful regarding testing the output of the Dynamo? Link to comment Share on other sites More sharing options...
DanMi Posted September 17, 2019 Report Share Posted September 17, 2019 I've often found that poor charging is down to the control box rather than the dynamo. The contacts corrode and then it doesn't charge properly. 1 Link to comment Share on other sites More sharing options...
poppyman Posted September 17, 2019 Report Share Posted September 17, 2019 Just check with a volt meter with engine running, no volts? no good..... You can have a duff new unit it happens a lot. Tony. Link to comment Share on other sites More sharing options...
daverclasper Posted September 17, 2019 Author Report Share Posted September 17, 2019 (edited) Thanks for that info guys. Just wanted to be certain I couldn't be doing anything wrong, as the tests on old and new unit gave the same readings. Also, I understand the dynamo is the first thing to check for a charging problem. Dave Edited September 17, 2019 by daverclasper Link to comment Share on other sites More sharing options...
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