not charging

[RDfella]

Am having enough grief trying to start my project, but some more has just arrived. Hopefully one of our resident electrical magicians can poinr me in the right direction before I get even more depressed. I have just converted my old ferguson tractor to 12v, mainly because there's little (no) choice in 6v batteries these days and finding one with enough oomph to start the engine is impossible. New dynamo, new regulator, 12v coil and dashboard bulbs. Fine. Starts great. But doesn't charge - light almost goes out then brightens again with increasing revs. Flashed the dynamo twice but no joy, so linked D & F on the dynamo and checked for voltage. It's all over the place - 18v, 3v, 12v, 0v, 18v. What's going on?

[groily]

I dunno RD, but a thought or two  . . .

The dynamo - regardless of what make.
Is it configured with the field coil connected with one end to the F terminal and the other to earth along with one brush (like a Lucas bike dynamo) or
is the field connected across D and F - with one brush going to D and the other brush to earth?

If the former, are you using a regulator designed to regulate with the field to earth? For example, a DVR2 works like that, as do the majority of after-market bike-type regulators (as they were designed with Lucas in mind). But a lot of car-types don't - and staying with the DVR range just for illustration purposes - the DVR4 doesn't.
These, JG regulators, and many others work on what I  call for simplicity the 'Bosch/Miller' basis - which is with the dynamo field coil connected between D and F.

If you have by any chance bought a dynamo with the field coil wired D to F, bridging those 2 and putting a meter twixt them and earth isn't the right test. The correct test for a dynamo wired that way is linking F and Earth, then testing for output between D and earth with a meter or suitable bulb.

Am assuming that if all the bits you've shelled out for are new, they ought to, er, work. So - just maybe? -  the output test applied is the wrong one? And if the units  don't work together could it be because there's a mismatch of the two methods?.

Like I say, 'dunno' -and there'll probably be someone along in a minute with better thoughts. But these are the first things I'd check out, given that your dynamo output test produced weird results.

The good news is that pretty much any pairing can be made to work, but the regulator determines how the dynamo needs to be configured.
Apologies if you've covered all these bases already  . . .  but by sheer coincidence, I'm converting a Miller for use with a 'Lucas-type' regulator this very afternoon, so it's all very fresh in my mind.

[bikerbob]

A couple of years ago I had that problem on my A7 it turned out to be the regulator it was an electronic one DVR2 type rang the guy at Dynamo regulators he said probably the regulatorand offered to test it but tookthe plunge and  bought a new regulator problem solved, you have a new regulator so maybe you could check that the conections are OK and wired correctly.

[RDfella]

All wired new (it's a simple 'loom') reg is mechanical 2 coil, but the wierd voltage fluctuation is at the dynamo with F&D bridged and all else disconnected. The brushes go to D and earth, field to F and earth. Looked closely at armature / field connections etc and can't see anything wrong. Never come across this before. Everything is new. Made in China Lucas repro I presume. PS it's the 11A version.

[groily]

Hmm.
Try squeezing the brushes gently while it's being driven, to see if they need a bit of bedding in, while doing the D&F bridge thing? That can steady the ship sometimes, until the brushes and comm get to know each other. Bit of electrical contact spray cleaner maybe as well?
If not that, then either a dodgy connection despite best efforts, or a fault on the commutator or armature windings I suppose, worst case. Hope not though, obviously.
Dunno about Chinese mechanical regulators, but it probably works if the dynamo would be gracious enough to feed it.

[chaterlea25]

Hi RD,
A lot of digital meters will go apeshit when connected to dynamo's or alternators
Test the dynamo with a 60watt headlamp bulb instead
A lot of the far away made mechanical regulators are rubbish, there are a few original Lucas S/H ones on ebay

John

[Swarfcut]

 RD, My first test would be the brushes. Do they conduct to the D and Earth connection, free to move, making good contact with the armature segments? A gentle polish with fine sandpaper of the carbon contact surface  of each brush is worth a go. Springs correctly assembled, holding brushes in contact with the armature segments.

 Then a continuity test of the field coils,  and the electrical connection to the body and F terminal.

 All good so far, finally check the armature for continuity and more or less the same resistance between adjacent segments, and segments opposite each other. Final test is that the spindle is electrically isolated from the armature windings. Open circuit from any armature segment to the shaft is what you want.

 Swarfy.

[RDfella]

Thanks for all that everyone. Whilst I've got it off and apart (again - about the 4th time now) I'll check continuity as swarfy says. Failing that, it's back on and try with a bulb as John suggests. Have to say I did wonder, giving the way the numbers were jumping about, whether the digital meter was insufficiently damped to get a reading. Might try a motor test whilst it's off as well. If the readings and bulb test are fine, guess it has to be that new regulator. On the other hand I might just use the dynamo as a belt tensioner and charge the battery from mains, which I have to do anyway, as it hardly ever gets used. Does seem a waste, though, given the new parts. But at least on 12v it's now a spot-on starter.

[Triton Thrasher]

It's all over the place - 18v, 3v, 12v, 0v, 18v. What's going on?

Don’t use a digital meter.

[edboy]

all dynamos like a good earth and the body sometimes needs a strap fitted to a good earth point. thats my experience. another time was a damaged commutator which caused the brushes to bounce.

[Colsbeeza]

Hi RDFella,
Sorry I cannot offer any advice, but commisserate with you. My 1958 Fordson Dexta does exactly the same. I purchased an aftermarket regulator about 16 years ago. Never fixed the problem, but remove and charge the battery after each use. I only slash (brushhog??) with it, so it gets around at 1600 rpm all day. Still not enough.
Col

[muskrat]

Bugga, this topic must've jinx'd me. Checked the 51 A7 and yep not charging. Probably dropped another belt. Will have to drop the 10mm setup for a 15mm. 
Cheers

[RDfella]

Happiness strikes. Spent this morning testing the dynamo. It was already apart (about the 4th time) from yesterday so I checked all connections, checked the armature including run-out of commutator in the lathe. Put it back together and into the vice to see if it motored. Which it did. So back onto tractor and give it the bulb test. Fine. So most of yesterday was wasted suspecting a faulty dynamo when in fact I’d been misled into believing that by using a digital voltmeter. Glad it wasn’t the dynamo as I couldn’t send it back as I’d already worked on it by replacing the front cover with a steel one in order to mount it (TE20’s have got an unusual mounting).
So, next step – look at regulator. Took less than a minute to find the wire to the A terminal was loose (small wire in a large yellow lucar terminal). I hadn’t crimped it tight enough. To think I wasted all that time chasing the wrong culprit.

But yet again thanks to you guys – not only does the huge reservoir of technical expertise throw up avenues to explore, but the mental support of knowing you’re not battling a problem on your own must not be underestimated either. 

[Greybeard]

 

[RichardL]

Bugga, this topic must've jinx'd me. Checked the 51 A7 and yep not charging. Probably dropped another belt. Will have to drop the 10mm setup for a 15mm. 
Cheers

When I ran the chain I never dropped a belt. Now I keep a supply of belts.

Richard