Ammeter blues - or electrics for dummies

A year or so ago, I said to a friend of mine, who happens to be a longstanding Yamaha dealer, that my old Norton had an electrical problem. He replied that a Norton WAS an electrical problem. I think that he is correct.

My 1970 Roadster has had a longstanding problem of losing charge, and being totally incapable of running for any time with the headlight on. Almost all of the time that I have been riding it – the last few years, the ammeter on the headlight (it is one of the earlier models that still has this) has had the needle firmly in negative territory; only when I am at highway speeds at about 4000 revs would it waver into positive. As the bike runs Boyer ignition this pretty soon translated into missing and stalling.

In order to resolve that issue I have recently installed a Sparx three phase alternator, and Sparx regulator rectifier. That was not without issue – the system initially did not put out the voltage that it should have. It transpires that the new spark plug leads that I bought and thought were not resisted leads – they are connected to 5000 ohm resister caps as recommended – were resisted leads – I have not tested them but the manufacturer’s helpline advised that they were resisted to about 900 ohms. With those leads on the regulator would only put out a maximum of 12.5 volts, and the ammeter still ranged between about -12 and -4 during most rev ranges. I have now changed the leads to copper leads – with the 5000 ohm caps, and that appears to have cured the problem; the regulator is now putting out 14.1 volts and 3 amps at idle, and 14.69 volts and 12.3 amps at between 3000 and 4000 rpm with the headlight on. The alternator is putting out about 15.5 volts from each of its three phases at idle, raising to over 30 volts at revs. So I am happy with my Sparx system.

However, the ammeter on the headlight still points to negative for most of the time, except when I am on the highway at 4000 rpm; when it fluctuates wildly but appears to hit positive. With the headlight on at say 2000 rpm it will show -12 amps. Is that normal? Or is it an indicator of a problem somewhere in the circuit that is taking all of the power that is being generated by the alternator and regulator? Or is it just what is to be expected to be used through the ignition system – and brake light; and headlight when it is on?

Could it be that the ammeter is defective, and if so, how can I test it? If I did not have the ammeter, as later models don’t, I would not be aware of any potential issue. I am not aware of any issues with the running of the bike – but since curing the spark plug leads issue I haven’t had the opportunity to go for a long run to see if any issues arise if I have the headlight on for a few hours. I am running a new 7ah battery.

How about sticking a real multimeter on it.

The local Harbor Freight has them for about US$3, so they can be had pretty cheaply.

That will tell you more than a 50 year old ammeter.

The ammeter is sort of an odditie. Mine bounces around until the battery gets charged up. I don't run with the headlight, just the running lamp, and never at night. I'm still using original rotor, stator, zener and rectifier. Mine starts charging around 3000. That said, a voltage reading or even one of the newer led indicators with the changing colors is probably a better indicator of the state of your battery, especially if you get an accurate voltmeter. If your battery is getting old, that will mess up readings too. Old batteries can suck up a lot of current that can be better used somewhere else.

Make sure you don't have voltage drops in any kill switch, the ignition switch, connectors, etc. Best way to check is voltage reading across things with ignition on and running.

Dave
69S

Frankly, I would do the voltage checks that you appear to have done and then either replace the ammeter with a new one or, preferably, bypass it completely. It sounds as if the output is OK from the alternator so all that's really necessary is to ensure all connections are clean. Remember that ALL elec power runs through the ammeter so any problem there becomes a problem elsewhere.

Cars used to have ammeters too but went to voltmeters because the ammeter itself and/or its connections can affect the entire elec system.

Re the spark plug wires...spark plug wires would not be expected to have any effect at all on output from the charging system. Are you sure that the only thing that was changed that caused the voltage to rise was the spark plug wires?

I would go through the entire elec system, breaking/cleaning/remaking all connections. After breaking them. clean the connections with something like De-Oxit and then coat the terminals with di-electric grease and re-connect them.

MexicoMike said:

Re the spark plug wires...spark plug wires would not be expected to have any effect at all on output from the charging system. Are you sure that the only thing that was changed that caused the voltage to rise was the spark plug wires?

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Insufficient HT resistance causes "overloading" of the Sparx regulator.
Sparx (Tri-Cor England) warn about this:
http://www.tri-corengland.com/acatalog/Alternators.html

**Single & Three phase boxes***
Due to the sensitive nature of both the single and three phase boxes it is VERY important to fit spark plug caps of the 5000ohm resisted type.
Failure to do so will cause overloading.

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So too much HT resistance may also cause problems.

I would say that if your Boyer started missing, then there probably is something going on and your ammeter was just telling you about it. If your wiring and switches are original then it wouldn't be wouldn't be much of a stretch. I installed an ammeter on my bike and it oscillated a lot till I rewired the loom, now it's steady. You might have a closed short or bad connection that isn't enough to pop the fuse but it's enough to drain current. What's the rating on the fuse you're using?
The thing to remember about ammeters is that they don't measure the output from the charging system directly, they only show how much current is going into or coming out of the battery. When the battery is topped off, which is almost all the time, the ammeter reads zero. It doesn't matter if it's 2000rpm or redline.

"
Insufficient HT resistance causes "overloading" of the Sparx regulator. "

Interesting! That's the first time I have ever heard of a spark plug wire affecting the output of a charging system. But clearly it is an issue with the Sparx. After reading the response I immediately went to the garage and ran the bike with resistance/non resistance wires, checking the load in both cases and there was no difference at any RPM with the oem Lucas electronic components/Lucas 3 wire alternator (180W as I recall). Wonder why there would be so much effect on the Sparx?

Do you still have the stock capacitor under the seat? I wonder if it is breaking down. As I understand it that results in a high resistance short. Which would only get worse as voltage climbs.
Russ

The thing to remember about ammeters is that they don't measure the output from the charging system directly, they only show how much current is going into or coming out of the battery. When the battery is topped off, which is almost all the time, the ammeter reads zero. It doesn't matter if it's 2000rpm or redline.

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Bob - are you able to expand or clarify that? Maybe I'm seeing questions that are not really there, but it is things like this that really show up my ignorance on electrical issues. I understand you to be saying that the ammeter measures output from the battery, as opposed to output from the alternator, which in turn in connected to the battery which is connected to the main circuit. I have wondered whether current from the alternator goes through the whole of the main circuit as well as the battery, but your statement suggests not - that it goes to the battery and the current from the main circuit is generated from the battery. If the battery is topped off ie fully charged -as mine is - brand new and most times hooked up to an intelligent charger - then it reads zero. Therefore when the bike is started and the coils are taking electricity to create sparks, and a light is on, then presumably it is normal for the ammeter to show a drop in available current - ie to hit negative - as some of the current is being used. But if so, then would not the battery put out more current to compensate and bring it back to zero, and if the battery is fully charged would not some of the current that is going to the battery from the alternator effectively be utilised to bring the main circuit back to zero or into positive? That should bring the amperage in the main circuit back to zero almost instantly?

Another thing that I struggle with (probably even more basic than electricity 101) is the difference between, and relationship between volts and amps, and after reading another thread on alternators yesterday, watts, and even ohms - and the relative importance between these measurements. I'm not asking for a deep explanation of this (I can go back to Wikapedia), but when testing the circuit for current with my voltmeter, what measurements should I be checking? Is the amperage that important?

Incidentally, I replaced the loom when I rebuilt the bike, so generally all the connections are good. I have taped over (as opposed to cutting off) the various connectors that I am not using. I think that my various earth points are good, but will recheck them.

Think of voltage as water pressure in a hose. Sometimes it's just sitting there doing nothing. Think of amps or current as the volume of water passing through the hose. When you turn on the end of the hose, it's like putting a load on it (resistance), sort of.

The ammeter will show a discharge when there are amps flowing out of the battery and a charge when flowing into the battery. If the battery is fully charged and you don't have a big load (headlight) on it, you shouldn't see much in the way of charge. However, if you turn the headlamp on you're immediately sucking amps out of the battery and if the charging circuit doesn't put out enough volts or current to overcome the battery voltage you will get discharge. As soon as the charging circuit meets the need (speeds up) for the headlamp, and the battery is not drained, you will get not much charging, but a headlamp will suck a lot of capacity from the battery pretty quick. that's why when you start up, you will get discharging and after a bit if the charging circuit is overcoming the drain, the charging will slow down.

I wonder sometimes when I see my ammeter flickering back and forth between + and - if the zener is switching between on and off state and the alternator is dumping current into it in a sporadic manner, making the meter flicker. I notice once I get going, the flickering stops. Could be just vibration too.

Dave
69S

Ammeter is not susposed to be wired directly inline with battery, but isolated
by another circuit, Assemulator?, that only allows current to flow in ammeter to show if more or less watts being consumed than produced but Not the total amount of current-amps flowing though system. Volt meter better to monitor which side of equation you're on. Trixie Combat has ammeter just to fill the hole, not wired but still wavers like normal just from engine vibes. Tough task to try to seal one to hold dampening oil w/o messing up the lens. There are small circuit boards available that allow only the excess hi or lo to show up instead of direct wire to battery that loses a few more precious watts, ie: pressure pushing amont of electrons against resistance.

Oh yeah there should not be any effect of ignition system on the charging or regulation as battery should isolate and dampen that small drain of maybe max 5 watt's intermittently. I'd also check the big blue can as mentioned as its a like a small battery too that absorbs spikes of charge and fills in for fast discharge dumps like horn and spark coils and winkers.

If he has a 70 (manufactured date) it has no assimilator, nor turn signals. If he'd put the points back on, the current draw to the points would be nil as long as they aren't closed, it can be pretty heavy if closed. The 68/70 wiring was pretty simple.

I'd still check out all the switches, connectors for voltage drop. Mine works fine after 3K rpm, and that's with a Pazon which draws about 4A as I remember. I also removed the lamps in the tach and speedo since I don't drive at night. Biggest draw on mine is probably the Pazon, followed by the brake lamp, followed by the rear light and the front pilot (unless I turn on the headlamp).

I did have an issue with the old ignition switch, it got real high on the resistance and took me a while to find it, but it can come apart and be cleaned, de-oxed and put back together with some #6 or 8 machine screws as I remember.

Dave
69S

Chris T said:

the ammeter on the headlight still points to negative for most of the time

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Hmm, same characteristics as the ammeter on my Triumph TR4A. The generator charges normally but the ammeter isn't sure what to do. I'd chock it up to the age of the ammeter and its inherent inaccuracies.

hobot said:

Ammeter is not susposed to be wired directly inline with battery, but isolated
by another circuit, Assemulator?, that only allows current to flow in ammeter to show if more or less watts being consumed than produced but Not the total amount of current-amps flowing though system. Volt meter better to monitor which side of equation you're on. Trixie Combat has ammeter just to fill the hole, not wired but still wavers like normal just from engine vibes. Tough task to try to seal one to hold dampening oil w/o messing up the lens. There are small circuit boards available that allow only the excess hi or lo to show up instead of direct wire to battery that loses a few more precious watts, ie: pressure pushing amont of electrons against resistance.

Oh yeah there should not be any effect of ignition system on the charging or regulation as battery should isolate and dampen that small drain of maybe max 5 watt's intermittently. I'd also check the big blue can as mentioned as its a like a small battery too that absorbs spikes of charge and fills in for fast discharge dumps like horn and spark coils and winkers.

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With the stock setup all the battery current (except for the horn) DOES pass through the ammeter, so if it goes open charging stops though a 2MC might keep the bike running. It is possible to convert to a shunt ammeter, if the gauge fails the battery still charges and the shunt (which is just a low value precision resistor) can be close to the battery to simplify the wiring. There is a good page on ammeters vs. voltmeters at
Broken link removed
I'm using a LED voltage indicator myself and it work well

THEY used to say , throwing a 6 to 8 inch wire across ( wired in ) let the ammeter do its thing , and if it didnt , it did . 8)

Chris T said:

I have wondered whether current from the alternator goes through the whole of the main circuit as well as the battery, but your statement suggests not - that it goes to the battery and the current from the main circuit is generated from the battery. If the battery is topped off ie fully charged -as mine is - brand new and most times hooked up to an intelligent charger - then it reads zero. Therefore when the bike is started and the coils are taking electricity to create sparks, and a light is on, then presumably it is normal for the ammeter to show a drop in available current - ie to hit negative - as some of the current is being used. But if so, then would not the battery put out more current to compensate and bring it back to zero, and if the battery is fully charged would not some of the current that is going to the battery from the alternator effectively be utilised to bring the main circuit back to zero or into positive? That should bring the amperage in the main circuit back to zero almost instantly?

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It looks like the voltage vs. amps as been explained pretty well. I like Dave's analogy of a hose under pressure (volts), and flow (amps). Unlike the water going onto your flowerbed though, the water has to go back to the sump for the pump, (battery and alt), to pick it up because its a closed system.

The battery and the alternator/rectifier-zener, are wired together like each side of a Y. The tail goes to the hot post on the ignition switch. The battery has about 13V and the output of the alternator is variable between zero and around 14V. If you turn on the ignition and hit the lights without starting the engine then all the power is coming from the battery and the ammeter needle moves to the left. When you start the engine and begin to spin up the alternator, it's voltage starts to climb and it's contribution increases and the needle moves closer to the center. When the output of the alternator matches the 13V of the battery, the needle is centered. When it goes over 13V then the pressure is higher than the voltage of the battery and the flow could reverse into the battery. But the thing about rechargeable batteries is that they will only charge to a certain capacity and that's all. If your battery is new and you keep it on a tender then it's full, and if the extent of discharge amounts to the time it takes for you to turn the key and kick it over and ride off then you're probably never going to see the needle move to the right very much at all.

You mentioned that the Sparz cured the problem, does that mean it stopped missing and stalling? What the charge on the battery when you get home? You do have the ammeter hooked up to the wire between the battery and the ignition switch, right? Not hooked up to the alternator like an assimilator? When people do that the ammeter usually has a life expectancy of about half an hour.

You mentioned that the Sparz cured the problem, does that mean it stopped missing and stalling? What the charge on the battery when you get home? You do have the ammeter hooked up to the wire between the battery and the ignition switch, right? Not hooked up to the alternator like an assimilator? When people do that the ammeter usually has a life expectancy of about half an hour.

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Bob, after rereading my original post I realised that I had not made it clear that the missing and stalling only (apart from one instance) occurred when I had been riding with the headlight on. After an hour or so if I came back to town and stopped in traffic it would stall, which I assume was because the battery was drained. The one occasion when it happened without lights on was when the bike had been stored and not ridden for some time, and I assume that I had allowed the battery to run down, and it did not fully recharge before I rode again.

No the ammeter is not hooked up direct to the alternator; the alternator and regulator goes direct to the battery, and the main loom comes off the battery - completely standard 1970 loom.

I didn't actually test the voltage on the battery after the last ride; the bike is at our beach place for the summer, and I did all of the testing down there with an auto electrician, because I didn't trust myself to do it properly and wanted to have some independent verification in case it did turn out to be a fault with the regulator; and I forgot to take my own voltmeter down there; I am hoping to ride again this weekend and will test it then.

Thank you for everyone's input. I think that I will attempt to test the resistance through the ammeter this weekend; I assume that I can do that by putting a voltmeter over it - set to amps? - and getting a reading as to the amount of current? I had a look at a video on facebook about testing regulators, and assume that the same process would work for testing the ammeter?

You can test the resistance of the ammeter by setting the VOM to ohms. Disconnect the battery while doing this. But it will be a very low value, probably less than 1 ohm and in the realm of where only a very good ohm meter can measure it with any accuracy. It would probably be better to measure the volts across it and then un-hook things, connect the ammeter in series with it and with the same rpm and lights check the amps. Since I=E/R, you will be able to calculate the resistance much more accurately. That said, if the ohm meter measures less than 1 ohm, it probably doesn't matter. I would just do the voltage check across it and if it's low, like below 0.5V forget it. If the ammeter needle indicates + and - while idling and revving, I wouldn't worry about it.

The voltage on the battery is a much easier way to test the battery. Charge it for a day or however long your charger says to fully charge it. Disconnect the charger and let it sit for a day and check the voltage. If it's 12.8 it's fully charged and holding good capacity. If it's down to 12.5V, it's getting marginal but still useful. If it's down to 12V, you're pushing it. Anything below that means the battery will not hold a good charge for any length of time. Of course this is at 70 deg F. Cold makes it lower and there are charts for that, but easiest to do it at 70 F.

You can also get a battery tester, they should be about $30 and there will be instructions with it.

Dave
69S

The ammeter on my Norton has always been erratic and reading from the neutral to minus amps and scaring everybody that rode it but not me! I figured out a long time ago that when I start it and turn on the headlight in the garage and rev it a little...... the lights get brighter removing all doubt about the ammeter and charging system. It's the nature of the beast.
Recently we bought an accurate kit Cobra with english instruments and the ammeter would not show a charge. After replacing inspecting and fiddling with the electrical system I realized that it was the same instrument as the 69 commando has and will never show a charge for whatever reason. Lucas, Prince of darkness

A 9V battery across the terminals of the ammeter will test it just fine, both ways. Actually the ammeter is just a voltmeter reading the volts across a very small resistance, so it should work or not unless the coils of the meter have been damaged or wires broken. Mine works just fine, but I don't use it as a reliable test instrument, just another indication, but it sure will tell me if my alternator wires are not hooked up. It reads everything except the horn.

I don't understand why people hate this little meter so much. I kind of like it, but then I'm a Luddite. I do wish and maybe will get some sort of volt meter to put on the bike so I really know how the battery is doing as I'm going along, like one of the led products. I just hate modifying the original state and it's working so good now, I don't want to mess it up. I guess it's kind of like a time machine for a 69 year old geezer.

Dave
69S