2a dyno failure, sparky help needed!

Eddy, I fitted an alternator to mine, but I also did a complete re-wire at the same time. The alternator is a straight swap in, but the wiring isn't especially as you'll be changing the vehicle polarity.

The alternator will include it's own voltage and current regulators, and the ones on the bulkhead are then redundant. I suggest that a change to an alternator, and getting some help to rewire.

Take a look at the regulator box, it's more likely that it's failed than the dynamo, although the dynamos do pack up as well. As for changing the dynamo, you'll need to polarise it the other way if it's come off a -ve earth vehicle.

If the above makes no sense, then I reccomend you get someone who knows electrics to have a look.

Alex

Thanks

It's probably the way to go but there's not much time at the moment. The long term advantages of an alternator and change to the universal -ve earth outweigh originality with this machine. It's an excellent workhorse and reliability is paramount. I may sort a temp solution out then go for alternator afterwards.

Thanks for the input so far, I'll keep you all posted when I have a mo. At the moment I have plenty charge in battery and only need short runs in daylight this week so it will wait til the weekend.

Never come across a failed voltage regulator before. Had several mini and morris 1000 dynamos pack up but never a v.r. .What do i look for in a failed v.r.? Burned out coils, shorted or dirty contacts. is a 'failure' usually repairable with sandpaper on contacts or is it a chuck out and replace operation? The dynamo is usually brushes if I remember, there's not much else to go really is there?

Is this an easy operation?

........for amusement, i've spotted that the odometer has just clicked over onto 66,666 as the dynamo/vr failed!

the number of the........

:-)

Eddy

In my experience the failure is probably the armature poling due to failure of the bush on the commutator end. (and failure to oil it!) Only solution is replacement in this case. It could, however be a stuck or worn brush, easy & cheap to fix. I have never seen a regulator fail in this way (usual regulator failure is either overcharging or flattening the battery due to failing to cut out). There is no difference between the positive and negative polarity dynamos except the polarisation. This is easy to do - after installation simply connect a wire from the battery to the output terminal of the dynamo for a few seconds. I have mixed feelings about changing to alternator - for is that positive earth means problems running any electronics, and the dynamo output is not enough to run much extra in the way of lights. Also the low output at low revs can mean the battery going flat in some driving conditions (lots of starts, slow driving and night use together). On the other hand, there is not really anything wrong with a dynamo, and there original 2as are getting rarer all the time. Mine has had an alternator for ten years, by the way. JD

On or around Tue, 6 Jan 2004 13:19:06 +0000 (UTC), "eddy bayton" enlightened us thusly:

dirty contacts is the favourite in the regulator, but only usually happens if it's either been left standing for ages or got wet inside.

brushes on the dynamo, or possibly failed field windings.

Hi Eddy, I had Dynamo probs on my neg earth 2A. IMO dynamos are pretty reliable and there is no point changing to an alternator unless you really want to spend a LOT of time messing about with the wiring. I'd also stick with +earth.

Its more likely to be a regulator fault, the regulator box is prone to electrolyte on the cut-out contacts. To find out, disconnect the wires from the dynamo-regulator box at the reg end and connect a side-light bulb between the dynamo feed and the chassis, this should glow at low revs and be pretty bright when you rev the engine (don't rev too hard!)

If you have voltage from the dynamo, proceed to the regulator box. open it, Check that the contacts are opening and closing corretly and clean the contacts with fine grade sandpaper. Finish up with a small squirt of WD40.

Sometimes it is necissary to adjust the regulator contacts by 1/2 turn to compensate for the contacts wearing down. This did the trick for me.

Thanks everybody for your help! Plenty of input from lots of people and all greatly appreciated.One of the most friendly and useful NGs around.

Problem was not the regulator in the end, nor the brushes, but the bearing at the pulley end of the dynamo. It had started breaking up and scattered bits through the windings despite still just rotating. The problem became apparent when I removed the dynamo as there was lateral movement and 'crunchiness' in the shaft. Popped down to my local and usually excellent Factors where they dug out an exchange unit from AC Delco. Perfect match and sheet of repolarisation instructions included. Good price. Great. Only problem no pulley on new unit. You know what's coming next don't you. Yep! Man behind counter says 'we'll have that off in a jiffy' , grabs his gloves and a Manchester Screwdriver (size 1) and disappears round the back. Noise of hammering off. Swear word. Returns with two halves of a pulley and says 'told you, didn't take a moment' rather sheepishly. He hadn't let me say 'Don't forget there's a woodruff key' even. The factors now have both halves of the pulley and both dynamos while they recify the situation and I'm doing the very small mileage necessary with a bungee rope belt between crank and fan. All in a days work.

Interestingly the noise I always thought was a rather roughish big end and turned out to be the dynamo and the motor purrs along very sweetly. I'm going to stay with the dynamo too as I had a quick check of the changes needed to go to -ve earth and didn't like the thought of so many 'temporarily' rerouted bits of wiring. As the vehicle is almost completely original apart from some different steel wheels and fw hubs, it would be a shame to change. The old dynamo still had it's factory chalk marks on it dating it as April 1966! Makes me think the 66,666 miles may actually be original.

Thanks everbody anyway and I'll let you know tomorrow or the day after when were 'charging' along again.

Good to see you have it resolved. Failure of the front bearing in my experience is rare - its usually the bush at the back! JD