By way of introduction, I am new to this forum & ride a 1993 Ducati 900 Superlight. Recently I noticed that the battery charging light comes on intermittently while riding. Typically, it will come on after about 3 miles of riding & remain on for maybe 15 miles. After that, I will automatically turn off for at least another 50 miles. The battery is new. The alternator seems to be functioning well since output to the battery will increase to about 15.5 - 15.9V at 3,000 rpms. However, this range of voltage seems a bit high. So I am wondering if I have a voltage regulator problem. I installed an Electrex RR51 regulator/rectifier unit several years ago. Interestingly, I read a post by GhostRider on this forum who suggested that the intermittently battery light issue might be a quirk with the Electrex unit. Any light that can be shed on this problem, would be most appreciated. Thank you kindly.
Have you checked the multi plug where the yellow wires join to the main loom, look for signs of corrosion and maybe overheating. Agree 15.5v or more seems a bit high, I was always told and have found around 14.7v to be the norm. Others may have different experiences.
'Any light' - I like that........ Check the connections between the Electrex RR51 wiring and the rest of the bike.......I suspect the white wire to white/red wire connection may need attention. Take a look below - I produced this diagram for my 750 after I sorted the reg/rec wiring which was a mess.
When I had a 1995 900SS the charge warning light started coming on intermittently. A few weeks later the regulator blew up big style with lots of smoke and melted encapsulation spewing out, leaving me stranded at the roadside in the dark. 15.5v - 15.9v is far too high, it's a wonder it's not blowing the bulbs. You should be seeing about 14.2v to 14.6v. I suggest you fit a new regulator and check the yellow wires to the alternator while you are fitting it.
Yes, yellow wires from the alternator to the regulator look fine. I unplugged & cleaned the connectors as well.
"Any light"...pun intended. I did indeed check the wiring from the regulator. However, I admit not checking the white-to-white/red wire which I assume goes through the indicator light on the way to the battery. Thanks for the heads-up.
Well, it appears that I have stumbled on the cause of the intermittent battery light issue. By rechecking the voltage output at the battery, the output was as follows: 12.5V @ 1,100 rpms, 15.8V @ 3,000 rpms & 16.0V @ 4,000 rpms. These seems to be way excessive. And, finally, when I removed the headlight for easier access to the regulator/rectifier wiring, I discovered that the plastic electrical connector to the headlight was partially melted. So, unless I have missed another contributing factor, the problem appears to be a faulty regulator/rectifier. Does this sound correct?
Yes, the regulator is definitely faulty and the headlight connector is a separate issue. It has melted because the contacts are dirty or corroded. The resistance caused by this creates heat which eventually melts the connector housing. Remember that a 55W main beam is drawing near 6A of current at only 12V. At 16V the current would probably be nearer 8A although the corroded contacts would reduce this a bit with the rest being dissipated as heat in the connector.
Derek: When I disconnected the connector from the headlight, visually the contacts appeared to be perfectly clean with no signs of corrosion. Since my regulator/rectifier will likely need to be replaced, I would appreciate any recommendations on a new unit. It seems like there are 2 aftermarket options: the Electrex RR51 or the ElectroSport ESR510s or the ESR515. Thank you for your help.
Well if the connector is melted it must be getting hot. The usual reason for that is dirt or corrosion. Light oxidation may not be immediately apparent but it would definitely be worth giving the terminals a clean. I'm not familiar with the Electrosport regulators but the RR5 1 has been around for a long time now. The general consensus these days is to fit a Shindengen FAH02AA MOSFET regulator. They run cooler and are much more reliable. They are designed for a 3-phase alternator but for a single phase alternator you just connect the 2 yellow wires and leave the other input pin unconnected. You will lose the warning light function though.
Thank you, Derek. I'm not sure that I want to forego the warning light since it alerted me to my present problem. I will continue to do my homework. Thank you again.
If the reg/rec is charging too high and you ride with headlight on, then I would say that is the reason for the headlight connector to get too hot and melt. However, on my 750, I fitted a battery monitor light and I noticed that at rare occasions it would indicate 'overcharge' when I was running without the headlight on at about 3000rpm. I could never get it to reproduce it when the bike was in the workshop. But the connector never melted, because as far as I could tell 14.5volts was the maximum output of the alternator.
Bit late to this and don't know either the bike or the Electrosport RR at all, so may be talking complete crap Just something I would do and @Arquebus could perhaps confirm if I'm right or just have my head up arse. It looks like from Arquebus's drawing the white wire is the regulator sensing line. So if it was me I'd make dammed sure that the connections on that wire to wherever it goes, possibly to somewhere near the fusebox or even better the battery, are both clean and secure. If it's not then there is a distinct probability that there would be a volts drop. The regulator sees a lower voltage than the battery or system is actually at. If that happens the regualtor allows the system volts to rise until its sensing line is at the correct voltage, which leads to an overcharging condition Presumably Arquebus only got an overcharging issue with the headlight off is because when it's on there is additional load on the generator it was servicing the headlight so there was not enough current left to charge the battery quicker so whatever the issue was never appeared. That doesn't explain his mystery, but generators usually have a constant output, so if the generator is not servicing things like lights and charging the battery the rest has to be dissapated as heat, via the reg/rec. This is also why it's important to ensure the earth connections are in good condition and the wire of sufficient gauge. Just a thought that's all
Just quickly following on from Old Jock's post above...........the white wire and the red/white wire are for the 'no charge' warning light - they run solely between the warning light and the reg/rec. (only the red/white with the OEM reg/rec). IIRC the circuit is completed by the blue/black wire which connects to No.5 fuse. The other side of the No 5 (connection E) fuse is a brown wire which also connects Fuses 2,3,and 4 (B,C and D) plus the main relay. The Electrex reg/rec which supposedly has an internal fuse, is wired direct to the battery with the red and green wires; basically knocking out the need for any other wiring including the big 30A fuse. However, if the wire with the 30A fuse is in good condition and the connections are good, there is no reason why it can't be used to connect the RR51 reg/rec red wire to the battery. With regard to the possibility that my 750s battery monitor was showing a very rare overcharge, could simply be down to the monitor's quirks. After all if you add something to any vehicle (cars or bikes) in the way of another 'instrument' you will find you end up looking at it more than is perhaps necessary - I recall many years ago, I fitted various gauges to cars like Ammeter, Voltmeter, Vacuum, Oil Temp etc etc etc..........I spent more time looking at them, than I did the speedo.
I have one similar to this one, you can see the light in your perifory vision without consciously looking. https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/201338527109
Thank you for the information. Other than the OEM reg/rec, there seems to be a few aftermarket alternatives (here in the States): the Electrex RR51 (presently installed); the ElectroSport ESR515 (which uses the OEM wiring harness) & the ESR510; and 2 options from Rick's MotoSport Electrics -- Model 10-001 & Model 10-001H using MOFSET technology. Now it's just a matter of making a decision.
