Has anyone any experience of the following, the alternator light goes on and off repeatedly, it can be on for a few minutes then of for a while. In eighty odd miles yesterday resulted in me jumping the bike to get home. I can't see me riding for over an hour on the battery only, however the light being on is obviously indicative of not charging. The battery is new and gives good voltage and holds a load on test, with fly leads to measure the output of the regulator or diode pack it reads just over 1 volt which would make sense if the light was always on but it's very often off for long periods. A new regulator is available as NOS but runs around £200 so a better understanding of the issue would help before I spend the money. The alternator output was good and no break down to earth through either lead which have been replaced resently. I understand that the voltmeter controls the light and it can be on at low RPM with the alternator loaded up I may splice in a voltmeter in the regulator output and ride the bike to gain a good understanding of the output but having had the bike for only a few weeks I have little experience of the system on a 1980 Duke? Thanks, Nick.
Hi Nick, I no longer have mine but it used to do this quite frequently for no apparent reason as the bike would always start even if left for a few weeks between rides. Not saying yours is the same but it might be nothing to worry about, just old Italian electrics.
These charge warning devices are notoriously unreliable. The one I have is a Ducati Elettrotechnica but the one shown in the diagram is a Motoplat and appears to be wired differently. So I left it off and fitted the negative earth version of one of these ; It works beautifully and tells me if the battery is overcharging as well as undercharging. They are available from http://www.improvingclassicmotorcycles.com/products.htm The guy who sells them is very helpful. I don't know about the Pantah but I'm sure that the charge warning light on the Darmah which uses the Motoplat charge warning device should on when the battery is charging. In the meantime check the voltage across the battery when the bike is running it should be about 14.0V ± 0.5V
Ok thanks will contact these people and put one in as you say it's the same as the Darmah so will be help full. Although are you implying that the charge light is ON when the battery is charging and OFF when not charging? Thanks for the help. Nick.
Can you perhaps confirm the function of the GEN light as below, that it cycles on and off when charging as this would explain everything in a nutshell. But runs contrary to every other thing I've owned? Nick with thanks.
I believe that's the case on the Darmah, possibly the same on the Pantah. @Pete1950 should be able to give you a definitive answer.
As far as I recall the light was usually off and if it came on while the engine was running it apparently indicated a charge problem . However in the case of my pantah there was no apparent charging problem , it was just a case of the light glowing intermittently .
On a Pantah, the light should be off while the engine is running normally, provided all is well, and it should only come on when there is a problem, such as failure to charge. But the device which controls the charge light is notoriously useless and frequently goes wrong. The light coming on is more likely to be a problem with the device than a genuine problem - and if there really is a genuine problem the warning light may well fail to come on!
Ok I understand if the battery is being charged and everything is well ignore the light, the recommendation to replace the "voltmeter" with a modern pattern part is beneficial but not essential. I will run a meter in series and see what is going on when the light cycles, if all good will look to see if a modern equivalent can be sourced for peace of mind. Thanks all invaluable help. Nick
I replaced the Regulator with a new one and this then dispensed with the voltimeter, all is now well and the battery is charing and the light function normal. I must mention that Andrew from MDINA was very helpful with the wiring up of the new reg and the supply of a new wiring diagram and assistance over the phone, thanks all. Nick.
Where the yellow wires from the alternator plug into the terminals on the regulator, I suggest you make doubly sure they are securely attached, are making really firm contacts, and there is no risk of them coming loose. An extra fixing of some kind is a good idea.
