Lucas e3l dynamo testing


  • DC Generator Troubleshooting
  • Testing a Lucas dynamo
  • Rex's Technical Support
  • E3L Dynamo Repair Kit BSA 6V
  • Electrical
  • DC Generator Troubleshooting

    Understanding how the Dynamo works will make your British motorcycling experience more satisfying and riding at night practical. The Dyno works in this manner. Battery voltage is monitored by the voltage control box. When battery voltage drops below 6. This creates an electro-magnetic field in the field coil.

    As the armature windings rotate through the magnetic field current is induced in the armature windings. This is transmitted to the regulator where another set of contacts that regulate current to the battery and electrical system. There are two basic types of Lucas dynamo. The model E3H , easily identified by the single large screw securing the pole shoe.

    The E3H puts out 45 watts and is stamped on the case with E3H. The later 60 watt unit is the E3L the field coil is secured by 2 screws on these units. It is important to know what type you have in order to select the appropriate load your dynamo can service. If you install a 45W headlamp and 21W tail lamp with a 40W dynamo it will be unable to keep up with the demand resulting in dim lights and a discharged battery. Factory recommendations were for a 6 volt 24 watt headlamp and 6 volt 3 watt tail lamp bulbs along with 1.

    As you can see the demand is less than supply so the battery remains charged and the lights are relatively bright. The same can be said for the 60 watt unit but you may run 36W headlamp and 6W tail lamp and 2W instrument light with sufficient current to keep the battery fully charged. This would be the first place to look if your battery is becoming discharged during use.

    The E3M uses a bushing on the commutator end while the E3L uses a miniature ball bearing. It is vital these bearings are lubricated.

    The drive end of the Dynamo has a bearing as well. The Unit must be dismantled to grease this bearing. On A10 and Triumph Dynamos there is an oil seal that keeps grease in the bearing. After long service it is a good idea to renew this seal Lucas and grease this bearing. Magdyno units have a slinger to keep grease in the bearing.

    It is also vital that the Dynamo case be well grounded to the engine cases. If the dynamo case has been painted remove a small patch of paint to ensure a good ground. You can test Dynamo output in this way: We assume positive ground for the following tests; reverse the connections for negative ground systems.

    Remove the D and F connections at the dynamo and bridge the dynamo terminals with a short piece of wire. Using a volt-ohm meter on the 50 volt scale, or a 6v bulb with test leads, connect the negative terminal to the bridge wire on the dynamo and the positive terminal to the dynamo body. Reverse connections for negative ground bikes such as Vincent and pre British machines.

    Start the machine and bring to a high idle. The volt meter should rise quickly to volts or the bulb should light brightly. It is possible to damage the dynamo with it wired in this way if the engine RPM exceeds If no reading is obtained try cleaning the commutator with contact cleaner or WD Do not use flammable cleaners such as carburetor spray.

    You may use a bit of very fine emery cloth to clean corrosion from the segments also. Do not hold the jumper wire there but just arc it quickly times.

    This will re-magnetize the pole shoe of the Dynamo. The Dynamo depends on residual magnetism in the field shoe to start the magnetic field.

    Reconnect the jumper wire and check again for output. Note; Some pattern armature brushes have proven to build up a non conductive layer on the working face, they may look fine but will not conduct current from the armature. Always fit genuine Lucas brush sets Lucas for E3L. These may be eased down with a bit of hack saw blade until they are. In either case the Dynamo must be removed from the machine for further testing.

    Clamp the Dynamo in a vise and then connect the positive terminal of a 12 volt battery to the Dynamo case. Connect the negative battery lead to the bridge wire between the Dynamo D and F terminals. The Dynamo should motor spin in the direction the unit turns on the machine. If the direction of rotation is reversed then swap the brushes in their holders and try the unit again.

    It should motor in the desired direction. If you needed to reverse the brushes it is possible the unit will now work.

    Refit to the machine and recheck output as described above. If output is still low you will need to dismantle the unit for further tests. To dismantle remove the commutator end cover and remove the brushes.

    Check the condition of the brush springs. These should hold the brushes in firm contact with the commutator. Disconnect the field coil leads. Remove the two long bolts that hold the generator together. The commutator end and bearing housing should be a tight fit. Slide the Dynamo body off the armature. The A 10 uses a taper to hold the sprocket and can be very stubborn to remove. Use a gear puller for this. The Magdyno and most others are a straight shank with two keyways and are easily pried off.

    Remove the threaded ring under the drive gear and gently drive the armature out of the drive end cover. You can do a test of the field coil the coil attached to the main body by connecting a 6 volt battery in series with a 6v 3w bulb and the field coil wires. If the bulb is very bright when connected through the field then the field is internally shorted and must be replaced. The bulb should be a bit dimmer than when connected straight to the battery due to resistance in the field coil windings.

    Using the same 6 volt battery and 6v 3w bulb, or a Volt-ohm meter, check for continuity between each commutator segment. The bulb should light brightly between any 2 segments. The bulb should not light between any segment and the armature body.

    If there are segments that fail the continuity test it is possible the field winding solder joint is at fault. Try re-soldering the wire where it joins the commutator segment. Failure of the bulb to light means the armature is faulty. If the bulb lights between any segment and the body of the armature it is internally shorted and replacement is needed. Do not attempt to straighten a bent armature or reattach loose commutator segments, it is false economy and will result in catastrophic failure.

    Reassembly is reverse of disassembly as they say. Make sure to fit the locking washers on the through bolts that hold the dynamo together. These tend to come lose and if they do the dynamo will be a complete write-off.

    Bill Getty.

    Testing a Lucas dynamo

    Top 1. Disconnecting the dynamo The easiest way to test a whether a Lucas dynamo is working correctly with it still fitted to the bike is to disconnect the output wires and check what voltage it is producing. The original Matchless service manuals suggest using an analogue meter i.

    However, I guess most people will probably have a digital multimeter these days and these are perfectly fine too. Whichever type you have, just make sure you connect the tests leads correctly as described below.

    The first thing you need to do is to disconnect the two wires which come out of the back of the dynamo and which connect it to the regulator unit, as shown in the photos. The two wires can then just be gently pulled out. I found the easiest way was to pull on the exposed ends of the brass ferules using pliers whilst also gently tugging on the wires. If you just pull on the wires, you might find that the cable breaks leaving the ferule stuck inside.

    The photo below shows the dynamo with the two wires removed ready for testing. Top 2. Connecting the dynamo terminals together Once the two output wires to the regulator are removed, you then need to connect the two dynamo terminals together using a short length of wire. Some thickish multicore copper wire is best such as the sort used for household wiring.

    Next bend the bared ends of the wires back on themselves and maybe spray them out slightly. You should now have a suitable link wire which can be inserted between the two dynamo terminals; the bent-over bared ends of the wire should be enough to make a good connection and hold it in place without using the brass ferules. Now you need to double check whether your bike is wired positive or negative earth. Simple as that! Top 3. Connecting the multimeter You now need to connect the two test leads of your multimeter between the Lucas dynamo and the bike frame to measure the voltage difference between the dynamo and earth.

    Conversely, if your bike is wired negative earth, then connect the negative black test lead of the multimeter to a suitable earth point on the engine, gearbox or frame. My bike is positive earth and so the photo below shows the negative lead of the multimeter inserted into the dynamo terminals. The earth point can be anywhere on some bare metal, but somewhere on the engine is probably best to ensure a good earth.

    I found that I could wedge the end of the test lead down the side of one of the engine casing nuts and this was enough to hold it in place long enough for the test. The other test lead i. You should just be able to put the test lead into the terminal along side the length of wire and that should be enough to hold it and give a good connection.

    Turn the multimeter on and set it to the voltage measuring range for 0 to 10v, or perhaps 0 to 20v on some models. Check that the meter reading is 0. Also make sure that you have it set to measure DC direct current voltages and not AC alternating current as a dynamo produces a constant voltage.

    Top 4. Starting the engine Now you need to start the bike. Note that it is very important that with the temporary connections we have made across the dynamo, that we DO NOT rev the engine too highly as this could damage the dynamo. Get the engine running and let it settle down to a normal tick over idle speed. Top 5. Checking the voltage output from the dynamo With the engine running at idle, the multimeter should be reading a couple of volts output from the dynamo.

    Gradually increase the engine speed to a fast tick-over and watch the multimeter. The voltage output should rise steadily with increasing revs, but DO NOT rev the engine so much that the output exceeds 10 volts as this could cause damage to the dynamo.

    When you release the throttle and the engine settles back to tick-over, the voltage should also fall back down to just a couple of volts. Also note the polarity of the voltages i. Top 6. What voltage readings should I get? When the engine is idling at tick-over, you should hopefully see a reading of around 1 or 2 volts, depending of course just how quickly you have the tick-over set.

    As you increase the engine speed up to a fast tick-over say around rpm , the voltage output should rise smoothly to somewhere above around 7 to 8 volts. The output needs to exceed the battery voltage i. There should be no need to race the engine in order to get this sort of output and remember that exceeding 10 volts or so may damage the dynamo. The charging system is designed to work i. There should be no need to race the engine to get a reasonable voltage output, otherwise the battery has no chance of being charged under normal riding conditions.

    Also, note that the voltage output should be positive i. Even though the Lucas dynamos were designed to work with 6v electrical systems, their actual maximum voltage output is much higher — 14 volts or more would be normal. It is therefore possible to convert the charging system to 12 volt operation and thereby charge a 12v battery without having to modify the dynamo at all.

    All that is required is to replace the original electro-mechanical voltage regulator with a modern electronic version. However it is not desirable to test the dynamo at these voltages with it connected as it is at the moment as it has no load on it and the two terminals are shorted together. Checking that it outputs up to 7 or 8 volts at a fast tick-over is good enough for now, irrespective of whether your bike is running at 6 or 12 volts.

    Top 7. Try giving them a wiggle whilst the engine is running and see if the meter reading changes at all. Lastly, check that the multimeter is set to read DC voltage not AC, current or resistance etc and is set to an appropriate range v or v say. Try measuring the voltage across the battery to check you get a sensible reading to be sure the multimeter is working. The service manual suggests that the cause of no voltage output is probably the brushes, but it might be worth completing the resistance checks described below to see if you can narrow down where the problem lies.

    It might also be worth trying to repolarise the dynamo, as is discussed later in this article. Low voltage output of approximately 0. The resistance checks described below may help to confirm this diagnosis, but either way the dynamo will probably need to be removed from the bike for servicing.

    Low voltage output of between about 1. Again, the resistance checks described below may help to confirm where the problem lies, then the dynamo will probably need to be removed for servicing. Negative voltage output — The first thing to check is that you have the test leads around the correct way as described in section 3 of this article.

    The leads need to go different ways around depending upon whether your bike is positive or negative earth. If the leads are correct, then it looks like the dynamo is incorrectly polarised and so is giving a negative rather than positive voltage output, just like my bike is doing in one of the photos above.

    Top 8. Measuring the field winding resistance Further checks can be conducted on a Lucas dynamo to confirm its correct operation or narrow down the source of a charging problem by measuring the electrical resistance of its internal wiring.

    To do this we first need to remove the multimeter test leads and also the temporary wire we inserted between the two output terminals of the dynamo. Change your multimeter on to resistance measuring mode and select the lowest range on my multimeter this was Ohms. You should hopefully get a reading of around 3. If there is less or zero resistance, then you might well have a short in the field winding. If there is a very high resistance i.

    My bike gave a reading of 3. I was more than happy with that! Top 9. The earth lead can remain in the same place. However, my bike gave a reading of On the other hand, my dynamo did completely fail about a year after I originally conducted these tests and wrote this article, so the higher resistance could have been a sign of problems developing.

    I guess if the resistance is anything significantly more than these sorts of readings then you might conclude that there are some bad connections somewhere within the dynamo. On the other hand, no resistance i. Similarly if you can provide further information, please leave me a message using the comment form at the bottom of this page.

    Top However, the multimeter does not impose any load on the dynamo and so such tests will not tell you how the dynamo will perform under-load i. Some faults may only occur under load with the dynamo appearing fine when nothing is connected. Other times you might get a good voltage output, but not enough current output to charge the battery and run the lights. A spare headlamp bulb of between about 25 to 35 Watts is probably best as this is close to the rated 45 Watt power output of the dynamo note bigger 60 Watt dynamos might need a bigger, say 50 to 60 Watt, bulb.

    The bulb should be 12 volt even if your bike is still set up for the standard 6v operation as the actual voltage produced is much higher. The bulb needs to be connected to the dynamo in exactly the same way as the multimeter was connected back in section 3 of this article for the first voltage measurement test.

    Start by re-fitting the jumper wire between the two dynamo terminals to join the Field and Dynamo coils together, then use a length of wire to connect this combined output to the bulb. A further length of wire can be used to connect the other terminal on the bulb to a suitable earth point on the bike, or you can simply touch the bulb base onto the engine to give the ground connection.

    But as you raise the engine revs not too high though! Remember that the dynamo voltage here is unregulated so the voltage is or at least should be! So it is easy to blow your bulb with too many volts if you rev the engine too fast.

    If the dynamo is working as it should, then the bulb should glow brightly without needing to race the engine. Instead, a magnetic field is induced in the Field coil inside the dynamo by passing current through it, thereby generating a stronger induced current to flow out of the Dynamo coil.

    In order to initialise power generation when the engine is first started, a small amount of residual magnetism needs to be left in the core of the dynamo from the last time it ran. This can correct the zero or negative output voltages that you may have come across when performing the multimeter measurements described at the start of this guide.

    Update: Output from a reconditioned dynamo Just a quick update to the preceding article concerning my own Lucas E3NL dynamo. My magneto stopped producing a spark recently so I took the opportunity to get my dynamo reconditioned at the same time as its output seemed to have become somewhat intermittent.

    It is therefore possible to convert the charging system to 12 volt operation and thereby charge a 12v battery without having to modify the dynamo at all. All that is required is to replace the original electro-mechanical voltage regulator with a modern electronic version. However it is not desirable to test the dynamo at these voltages with it connected as it is at the moment as it has no load on it and the two terminals are shorted together.

    Checking that it outputs up to 7 or 8 volts at a fast tick-over is good enough for now, irrespective of whether your bike is running at 6 or 12 volts. Top 7. Try giving them a wiggle whilst the engine is running and see if the meter reading changes at all. Lastly, check that the multimeter is set to read DC voltage not AC, current or resistance etc and is set to an appropriate range v or v say.

    Try measuring the voltage across the battery to check you get a sensible reading to be sure the multimeter is working. The service manual suggests that the cause of no voltage output is probably the brushes, but it might be worth completing the resistance checks described below to see if you can narrow down where the problem lies. It might also be worth trying to repolarise the dynamo, as is discussed later in this article.

    Rex's Technical Support

    Low voltage output of approximately 0. The resistance checks described below may help to confirm this diagnosis, but either way the dynamo will probably need to be removed from the bike for servicing.

    Low voltage output of between about 1. Again, the resistance checks described below may help to confirm where the problem lies, then the dynamo will probably need to be removed for servicing. Negative voltage output — The first thing to check is that you have the test leads around the correct way as described in section 3 of this article.

    The leads need to go different ways around depending upon whether your bike is positive or negative earth. If the leads are correct, then it looks like the dynamo is incorrectly polarised and so is giving a negative rather than positive voltage output, just like my bike is doing in one of the photos above.

    Top 8. Measuring the field winding resistance Further checks can be conducted on a Lucas dynamo to confirm its correct operation or narrow down the source of a charging problem by measuring the electrical resistance of its internal wiring. To do this we first need to remove the multimeter test leads and also the temporary wire we inserted between the two output terminals of the dynamo.

    Change your multimeter on to resistance measuring mode and select the lowest range on my multimeter this was Ohms. You should hopefully get a reading of around 3.

    If there is less or zero resistance, then you might well have a short in the field winding. If there is a very high resistance i.

    My bike gave a reading of 3. I was more than happy with that! Top 9. The earth lead can remain in the same place. However, my bike gave a reading of On the other hand, my dynamo did completely fail about a year after I originally conducted these tests and wrote this article, so the higher resistance could have been a sign of problems developing.

    I guess if the resistance is anything significantly more than these sorts of readings then you might conclude that there are some bad connections somewhere within the dynamo. On the other hand, no resistance i. Similarly if you can provide further information, please leave me a message using the comment form at the bottom of this page. Top However, the multimeter does not impose any load on the dynamo and so such tests will not tell you how the dynamo will perform under-load i.

    I had trusted the dynamo supplier to have marked up the dynamo correctly and that was the fault. The error was only easily visible when the tie-wrap holding them all together had been snipped. Interestingly, if I had bought an old dynamo and overhauled it myself the whole charging issue would not have occurred as I would have marked it up correctly as I did on the Model Although very cold the roads were largely dry and I was determined to perform a road test.

    I headed off via Witney into the Cotswolds and covered some 40 miles, all the time registering charge on the ammeter with lights full on.

    Such a sense of satisfaction knowing that I should now not break down from a flat battery. As a precaution the loading ramp had been placed in the big van and I had a well charged mobile phone with me. Nice bloke Mike. Battery voltage is monitored by the voltage control box. When battery voltage drops below 6. This creates an electro-magnetic field in the field coil. As the armature windings rotate through the magnetic field current is induced in the armature windings.

    This is transmitted to the dubai porta potty video where another set of contacts that regulate current to the battery and electrical system. There are two basic types of Lucas dynamo.

    E3L Dynamo Repair Kit BSA 6V

    The model E3Heasily identified by the single large screw securing the pole shoe. The E3H puts out 45 watts and is stamped on the case with E3H. The later 60 watt unit is the E3L the field coil is secured by 2 screws on these units. It is important to know what type you have in order to select the appropriate load your dynamo can service. If you install a 45W headlamp and 21W tail lamp with a 40W dynamo it will be unable to keep up with the demand resulting in dim lights and a discharged battery.

    Factory recommendations were for a 6 volt 24 watt headlamp and 6 volt 3 watt tail lamp bulbs along with 1.

    Electrical

    As you can see the demand is less than supply so the battery remains charged and the lights are relatively bright. The same can be said for the 60 watt unit but you may run 36W headlamp and 6W tail lamp and 2W instrument light with sufficient current to keep the battery fully charged.

    This would be the first place to look if your battery is becoming discharged during use. The E3M uses a bushing on the commutator end while the E3L uses a miniature ball bearing. It is vital these bearings are lubricated. The drive end of the Dynamo has a bearing as well.

    The Unit must be dismantled to grease this bearing. On A10 and Triumph Dynamos there is an oil seal that keeps grease in the bearing. After long service it is a good idea to renew this seal Lucas and grease this bearing.

    Magdyno units have a slinger to keep grease in the bearing. It is also vital that the Dynamo case be well grounded to the engine cases. If the dynamo case has been painted remove a small patch of paint to ensure a good ground. You can test Dynamo output in this way: We assume positive ground for the following tests; reverse the connections for negative ground systems. Remove the D and F connections at the dynamo and bridge the dynamo terminals with a short piece of wire.


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