On my 1990 Yamaha FJ1200 I use a radar detector as a volt meter. Lately the voltage has gone up .5v over the rev range, still within tolerances. The really weird thing is that at cruising speed when I hit the brakes or the turn signals, the voltage goes UP .4v-.5v. It does not go up when switching to hi-beam. Is this a symptom of impending reg failure? Or what? THX in advance. Matt
It sounds to me like symptoms of a bad ground. Good for you for noticing this too! Anyway, you could start by going over most of the grounds, just a loosen and tighten type of thing and make sure you electrically follow the path to the alternator as well. It could also be only affecting the circuit your detector is connected to, so check that one thoroughly as well.
Thanks greasemonkey. I' had planned on checking the connectors today. I'll add the grounds to the list.
Besure to compare to Known Good voltmeter, dash mounted devices are known to off by .5 to 1.0 volt. There maybe nothing to worry about. Use a good digital voltmeter like a Fluke etc checking over wide rpm range with changing loads.
Yep , did that. Using a digital voltmeter the voltage at the battery is consistantly .5v lower than on the radar detector. I've known this and take it into consideration. My voltage is still where it should be but, as I said, creeping up. What would cause the volts to go up when braking or signaling??
Focusing on just the voltage spike linked to the brake lights & signals and disregarding the other constant voltage increase it may be caused by the way the VR senses the voltage to make adjustments..... There are several circuit designs based around the design of the VR. Some VRs have internal sensing and no dedicated sensor wire. Some have a sensor wire that goes directly to the battery +. And some (like my 99 F 650) have a sensor wire that goes to a switched circuit up in the dash somewhere and electrically far away from the battery. This last type is basing its voltage output on that distant switched circuit which is also directly feeding changing loads like signals, brake lights, etc. So, when an extra bulb or two gets lit, the sudden IR or voltage drop is sensed by the VR which responds by spiking up the voltage to compensate. I see the effect on my F 650. Then usually when you don't see a similar spike when switching headlight beams, its because they are fed directly from the battery through a relay, so the voltage over on that switched circuit doesn't see the drop/increase at the battery terminal like it does the changes in load on the circuit it is "sensing". Make sense? Back to the overall increase of .5V ..... The only two VRs I've had fail in about 4 decades both showed slowly rising voltage from about 13.5 up to 15+ over a span of several minutes. Then a sudden drop back to the normal 13.5 or so followed by the slow steady climb back up. One was on a mid 70s Porsche 914 and the other was the OEM VR on my 95 Ducati M900. So I woudn't worry about impending failure at this point, but keep an eye on the range it stays in.
You may have a bad wire or terminal between your battery and alternator. This would show up with a voltage drop between the 2 components. You could try to piggyback a #10 gauge wire between the 2 and see if that brings the battery voltage up. You might also want to put the battery on a trickle charge overnight which doesn't fix the problem at all but can help you diagnose it.
Humm Explanation of voltage going up with increased load ... battery remains at same voltage .. As the load current increases so too will any voltage drop across any series resistance .. Humm .. no that does not work .. What kind of alternator / voltage regulator is there on your bike.. if the alternator is a permant magnet rotor type then chack how hot the rectifier/regulator is .. if hot then you are looking a buying a new one now. Check how hot the battery is too .. this is after a run .. Err .. does the bike start ok? If it is marginal ... does the battery still have water in it? (thinking the regulator/rectifier may be shot and the increased load is helping rectify the alternator output .. ) If it is a faulty ground then run another ground wire - say from the earthy side of the stop light to a good chassie connection - should eliminate that from the guesswork..
sorry, unless you are getting down to the thousandth of volts, this is not really true. Even cheap DVMs work well these days.
I never got an email notifying me of the last couple posts:huh I'm trying to fix/diagnose this while commuting(on the bike) 100miles/day, working 10hours/6days plus the honey-do list. That said, I'll check the temp of the battery and RR tonight when I get home. Bike starts fine. And I'll try a better ground on the taillight.
Probably the regulator or corroded wiring/connectors somewhere. The regulator controls the alternator output based upon load and excites the alternator as apprpriate to increase output. Corroded/screwed up wiring can cause this as well as a bum regulator. Start looking for green mung on connectors and shit on a bike that old.
Reverse EMF? When a voltage is applied then interrupted to a circuit containing a coil, for example a relay, a voltage spike or reverse EMF is emitted. The same principle is used in the ignition coil. A flasher relay has a coil inside, but doesn't really explain the brake theory, unless it has ABS. http://www.fas.harvard.edu/~scdiroff/lds/ElectricityMagnetism/BackEMF/BackEMF.html
I won't try to go into a long winded defense of my statements about the voltage drops/spikes associated with brakelights or signals. Its free advice about what it could be - so it's worth what it costs. But since a few folks are skeptical, I do want to clarify that scenario is only valid if the VR is of the type with a dedicated sensor wire that picks up its voltage from a switched circuit up near the ignition switch or dash. And it is a "maybe" type explanation. I don't work in the field now, but I do have training and work experience in AC/DC electronics. And a lot of experience with bike stuff. If you measure the voltage at a convenient point up under the dash (like ignition switch) on such a setup you will often find the votage is lower by maybe .5V or more than at the battery + terminal. And because it is electrically "remote" from the battery it sees more voltage fluctuations than at the battery. That is the reason many many F 650 Fuduros cook the water out of their batteries - the VR senses say 13.2V at the dash, but the battery may be at 13.8V. The VR sends enough voltage to the battery to raise its sensor wire voltage to 13.5 nominally, but the battery is really getting more like 14V or more directly from the alternator which overcharges and cooks water. BTDT on mine, like so many other F 650 owners. The later EFI models have VRs with internal sensing which eliminated that problem. There's lots written about it over on f650.com FAQs(some by real EE types) including a cure which involves relaying the sensor wire almost directly to the battery. But that is way beyond what's under discussion here. Anyway, my statements may or may not apply depending on the type of VR on that bike and how it senses the operating voltage. For example, my Ducatis both now have aftermarket VRs that have internal sensing and no separate or switched sensing wires. They don't behave like the F 650 setup. Sorry, it got long winded anyway. But just trying to clarify in case it helps any. I did see one comment that I respectfully disagree with. Most bikes have a permanent magnet type alternator(cheaper for manufacturers) and the VR has no excitation function WRT the alternator. The raw output of the alternator windings are purely a function of RPM. The VR adjusts the voltage to maintain the operating parameters by drawing enough current off and dissipating it as heat through the heat sink fins. Now, if a system uses an alternator with both wound rotor and stator and no magnets, then a whole different VR system is used which does control voltage by controlling the excitation feeding the stator or rotor (usually stator in those types). A vastly superior system from an electrical design standpoint, but more costly than the permanent magnet type alternator.
<BR>That's just silly. Tapping the VR sense voltage from a location that provides a sense voltage significantly different that the battery voltage. Hey Mark you may know this. Do you know if anyone is making a VR for a permanent magnet alternator which uses pulsewidth control on the 3 alternator primaries for voltage regulation? Call it a 3-phase buck regulator? <BR><BR>
No clue as to whether anyone has a design based on pulse width control. I've never looked closely at the internal circuits workings, just more on the general types and how they wire up. I would imagine such a VR would be very similar in function and design to an A/C motor speed controller, and as such could be relatively cheap. Still has to meet the cost effective challenge to get into the marketplace. But there may already be some one-offs built by tinkerers.
<BR> Ahh heck. I thought you may have seen, or maybe knew of one. I mean, your knowledge of moto charging systems is obvious. And yessir, a high frequency AC motor drive is the essential part of the circuit. <BR><BR>
Most but not all ..bms MotoGuzzi .. to name two manufactures.. Just cover the bases incase. Poolside .. you know that it is the new EE (fresh out of school) who designs the power supplies while the 'old' hands get to the 'interesting bits' ... Then the Production E come along and removes things untill it does not work . and then puts the last thing back in. Reliable under all conditions?
+1 grounds can do weird things once had a chevy van that the lights would get dim, unless I held the column shifter up ground strap was corroded and the shifter linkage was making another ground path thru worn out bushing ... had me stratching me head fer sure but I was a callow 18 or 19 back then too
