Low Alternator Output

One thing you could check is whether the rotor has de-magetised.

While I have no knowledge of how the stator is wound, an open circuit sounds wrong to me.

I've learned from here that the Wipac and Lucas rotors have different diameters. Has a previous owner put a 'wrong' stator (Lucas?) on? Excessive clearance will mean low output.

How big is the clearance you have? Ideally around .008" (0.2mm) is what you are aiming for.

Good luck in your search for the missing volts 

George 

Hello David. The simple test has always been whether the rotor will 'stick' to a screwdriver blade under its own weight - if not then it's weak. When you say the resistance between the orange and white wire is 0 ohms do you mean a full short circuit or an open circuit?

Hi David,

If you have 0 ohms between the any pair of wires, the stator is scrap.

When you say 0, do you mean a dead short? Either way, it is scrap.

Tony

Hi David,

Re:- On other comments, zero ohms means no resistance. An open circuit would be infinite resistance.

Yes, I know that but not everyone understands that.

So it is a dead short. Unless you can see and remove the short, the stator is scrap, however strong the magnetism is.

Tony

Hi David,

You need to see some resistance. 0 ohms could mean one if 2 things  Either the coils have shorted out internally, or you are using the wrong scale on your multimeter. Of course you do need continuity  which might be what your meter is telling you, but there should be at least some resistance. Somewhere around 0.6 or 0.7 ohms isn't unreasonable. If your meter on its lowest resistance setting is saying 0.00 ohms, then it suggests that there is a short circuit within the stator somewhere.

Are you able to see where the wires begin and end for each coil and measure each coil? If so, you can at least compare each with its neighbour.

Hope this helps,

George.

What a lot of misinformation. Why didn't some body call me?

To start at the beginning. David says he has 2.5V ??? What is this? Our Lucas and Wipac alternators generate a very nasty shape AC of variable frequency and hence despite giving some indication on an AC range it is VERY unreliable. There is a much better system of measurement on AOSERVICES.CO.UK. But the facts. Resistance between any wires will be 1.5ohms to 3 ohms ish. there shall NOT be any connection to the metal work.(earth of the bike) Attempting to read each coil resistance will be hard as the wires are varnished, sleeved and oily.

There is NO earth connection, the WHITE wire on the Wipac does the same job as the WHITE/GREEN on the Lucas it is a COMMON. Lucas has GRN/BLK as a low output. and GRN/YLW as High output. The Wipac has a Light Grn and an Orange these give 50/50 outputs.    But the same test system works, use a headlamp bulb across any two wires and as long as you have a bright lamps then the alternator is working. The only test for full current output worth doing is, connect up the original type silicon bridge rectifier (round black Lucas thingy), to the alternator. use a 10ADC meter between the rectifier output (negative) and the bikes wiring, tun on the lights. Rev engine. Full output should be seen on the meter (RM 19/21-9Amps).

Here endeth the first lesson.

If the DC o/p from your Reg/Rect is low, then the AC input will also be low as the reg/rect holds the alternator down. One test I didn't mention before was/is if the reg/rect is suspect (as above) then replace the reg/rect with a full wave bridge rectifier as you had on the bike before. Either avail yourself of a new encapsulated item or refit (temporarily) the round black Lucas item you removed before. Use this to power the bike charging system as normal. Start engine, monitor DC to the battery, no regulation should rise to 15V or more. Put full lights on battery voltage should still be above battery at rest. Alternator would be in good order.

Yes, coils insulation has worn and you have leaks to earth.

As Al says...

Why did no one contact me? Sadly, I gave up looking at the Forum a long time ago.

Too many opinions, some right, some well meaning, but wrong - how do you tell the difference?

Any query on a Lightweight Norton - (Jubilee/Navigator/Electra) - Write to me in the 1st instance - I may well have the answer - my details are in the back of RoadHolder.

From above:

Test for Rotor (the magnetic bit) is (as Mark says) will it hang off a spanner, supporting its own weight. Check each segment.

Wipac colours are White, Orange & Green.

There are at least two versions of stator (the bit with coils).

Each has six coils of about 1/2 an ohm each, so will show 0 ohms on most meters, as its almost a short circuit. You need a VERY sensitive meter to check this level of resistance. Your meter leads (& connectors) may have more resistance than this!!

The coils are wired (Jub/Nav) as 3 coils + 3 coils, and for Electra as 2 coils + 4 coils.

The white wire is common to both sets, so expect to read 1 ohm (Electra) or 1.5 ohm (Jub/Nav) between White and Green - and 2 ohms (Electra) or 1.5 ohms (Jub/Nav) between White & Orange - if all is well.

Then, of course, expect to read around 3 ohms between Green & Orange.

Last test is on a very high range - there should be no connection from any wire (does not matter which) to the body of the stator. By 'very high' range, I mean one that will register if you grasp both probes (don't worry - you won't feel it) as it can show your skin resistence.

ideally, the reading should be Infinity - no reading at all on the meter.

In practice, I have observed a reading on very old alternators that still perform well - as long as this reading is very, very high - upwards of 500,000 ohms - or 500kohms

This Electra Stator and A reg1 are in full working order. Maximum voltage obtained 14.4V. And maximum power at 12.4V 70W  (limit of test rig)

This shows up the problem of attempting to use a Multimeter without a full understanding of electricity and the wonderful ways of Wipac (and Lucas). Best to ask the knowledgeable ones. Thanks Andy.