Dynamo Failure?

[Packedup]

Spent today trying to get the ignition warning light to go off on project pickup.

I discovered if you really rev it the light dims, so I hooked up my volt tester. At fast tickover it gives about 2 volts, loads of revs it gives 4. This is after cleaning things up as much as possible without taking the end off, as the screws are well and truly stuck in there (broke a rather good screwdriver trying).

I have set it to negative earth, but I've done the small terminal to pos for a few seconds thing so I'm hoping this isn't the problem. Also tried about three other units, all similar or lower readinds...

I am right in thinking this is dirty brushes or other general dynamo fault, aren't I? Or should I be looking elsewhere?

[Willie]

If you cannot undo the two long end plate screws with a screwdriver
then remember that the screw heads protrude from the plate so,
if you do not possess an impact screwdriver ,
you can get Mole grips or pliers on the heads to loosen them off No, 3volts is not
enough!! Be careful when checking the dynamo output, you should
not need to increase the revs over 1000 rpm to obtain a good voltage
with the 'D' and 'F' terminals joined together with a short piece of wire.
Do not let the voltage reach 20 volts.

[Packedup]

Oh, for 20 volts! Well, OK, not quite 20, but a fair bit more than 4 with the engine red lining would be nice!

Couldn't get my cheap n nasty tools to grip the screw heads at all, so today I'm going to try the last couple of spares I dug out. If they don't work I do have a good Triumph one, but th epulley fouls the lower mount, and refuses to come off so I can swap it for a Minor one. It's getting annoying as all this playing with electrics is flattening the battery, but the engine can't be all bad as it fires first compression stroke on the handle

All part of the fun I suppose

[Packedup]

OK, after much grunting and swearing, I got the pulley off the Triumph one, and fitted a Minor pulley (and fan, as it was the fan that was fouling the Minor mountings), and got it all on. Same flippin problem!

Didn't check the actual output at the dynamo end though, by the time the battery was charged enough (front panel is off for painting) there wasn't a lot of time left to test everything.

It's looking more and more like regulator fault, and I'm getting closer and closer to ditching the antiquated system and putting an alternator on. Only problem there is remembering how to wire it up, and finding a bracket. Oh, and going to the breakers to chop a plug and bit of wire off.

We've got about half a dozen regulators, all giving the same fault, but the wiring all seems to be OK (haven't got a multimeter, just a voltmemter). Where do I start looking on a regulator in terms of checking connections and so on? Is it just the points that need cleaning?

[rayofleamington]

Please let me know what you find - I found the same problem on a project car 10 years ago and will have to fix that eventually

[Packedup]

Well I might put an extra day in tomorrow and see if I can sort it - It now cannot (should not?) be dynamo, so it leaves wiring and regulator. My current money is on regulator and or/ the various contacts.

I can't figure out what else it might be, there's obviously a good 12v going into the small spade as otherwise the ign light wouldn't be on. The car is now neg earth, but the dynamo fitted came off a neg earth car. It turns freely and worked 100% when removed, is also in clean condition. If it's not the regulator or a failing wire buried in the loom (unlikley, but without ohms tester I can't be sure) then I have no clue whatsoever

Wish I'd picked up the wiring diagram to study this evening, might have helped!

10 years eh? So far it's only been 3 and a half for a couple of my cars, and one has now cost more in storage than it would be to pay someone else to restore it! Might have to wave bye bye to it for the greater good of the others at this rate

[Willie]

To check the dynamo voltage output you disconnect the leads
to the 'D' and 'F' terminals on the dynamo and then join the two
terminals together. This of course, means that you have removed
the control box from the equation so,if you do not get a satisfactory
output from the dynamo in this condition then it has NOTHING TO DO
with the control box!

[Packedup]

The new (well, old, but known working) dynamo is now putting out a far too healthy x volts at the brown/ yellow wire on th ebox. I know this as my tester goes to 16 volts, and it's bouncing off the scale. I also thought I'd had success earlier, as the light was out. Then I found out it was because it had blown

So I'm gettig stupid voltage now, which I suppose is an improvement on 1 or 2 volts, but still not ideal. I've tried adjusting the regulator, I can get either 4 volts, or off the scale, nothing in between. And revving the engine makes the bulb brighter, in a whole it's getting a hell of a lot of power going backwards through it kind of way.

Methinks it must be regulator at this stage, as quite clearly what's happening is the dynamo isn't being regulated! But before I carry on with that thought, could wiring be an issue? Poor earths, flaky dynamo wire (the small one), that sort of thing.

This is absolutely doing my head in, that alternator sat on a shelf is looking more and more tempting, even if it does mean getting a bracket and macking up a harness...

[Willie]

If you check on the regulator you will see that there is a black wire
on terminal 'E'. this wire goes into the vertical loom on its right.
It emerges BEHIND the loom a few inches lower down where it is
earthed under a bolt head. This is usually out of sight so is neglected
and it is important that this earth is a good clean one. Have a look.
I would never recommend fiddling with the control box settings, apart
from cleaning the contacts.

[Packedup]

Ahhh, I did wonder where that earth went to, as the loom isn't fully fitted yet (testing it as I go, so if it's fundamentally flawed it's easier to remove and replace). So there's a very good chance my symptoms would be an issue if the other end of the black wire wasn't earthed? If so, then that's something I can look straight into, as I took it for granted all black wires were connected, and I know some of the earths haven't been cleaned and done up yet.

Thanks for the advice, I'm not bad with electrics but I've had next to no experience of regulators so I'm very much in the dark with this bit of the job!