More strange charging symptoms

[12jslater]

I've had multiple issues with my big seven charging, when switched on the ignition light glows happily, reads just barely bellow zero amps when running and the light stays on until the engine is revved and then goes out, my ammeter registers a charge, however when the revs go back down to idle the ignition light stays off and the ammeter dips to a discharge of around 5-10 amps??

Rather confused, this cars electrics are throwing up one thing after another haha.

[Howard Wright]

Hi

I’m no electrics expert but the behaviour doesn’t sound too far from normal.  I think the warning lamp is not directly on the charging circuit so will display different characteristics to the ammeter.  My worry would be the 10 amps discharge at tickover With only the coil taking current you should have about 2 to 4 amps discharge. Any more and something else is connected up.

Cheers

Howard

[Stuart Giles]

The ammeter going into discharge at tickover is usually caused by the cut out contact sticking shut with the result that battery current is flowing into the dynamo. I would make sure that the earth connection is good on your regulator, as the reversal of current flow should cause the cut out to release.

[JonE]

Could a fault in the dynamo itself also cause the light to stay extinguished? I have quite similar symptoms now! I've checked 'earth' to ignition light (to PLC switch) but am getting same high discharge and no light when ignition turned on. Light was operating fine initially and discharge nothing to speak of when ignition turrned on.

[Stuart Giles]

Could a fault in the dynamo itself also cause the light to stay extinguished? I have quite similar symptoms now! I've checked 'earth' to ignition light (to PLC switch) but am getting same high discharge and no light when ignition turned on. Light was operating fine initially and discharge nothing to speak of when ignition turrned on.

have you checked the bulb side of the circuit by disconnecting the wire from the dynamo's D terminal and touching it to a good chassis connection? The bulb should light if the ignition switch end of the circuit is good. The ignition light has battery voltage behind it via the ignition switch it and the dynamo D connection in front of it. When you turn on the ignition the bulb illuminates to earth via the non charging dynamo, when you start the car the dynamo output rises and the bulb dims and then is extinguished as the voltage rises.

The big discharge the OP is seeing is almost certainly caused by a sticking cutout where the battery is sinking power through the dynamo's armature when the dynamo's output drops.

[12jslater]

Unfortunately the regulator is a new electronic one that came with the car, so points sticking won't be an issue, I hope there isn't any issues with it as these electronics aren't exactly easily repairable given the biggest things on the circuit board is about the size of a grain of rice haha

[JonE]

JSlater - have you checked with the maker, as they are normally pretty up on troubleshooting their specific systems? Is it an AO one?

Stuart - many thanks. Will troubleshoot that. I haven't had the dynamo off (but have got super new earth returns and strap to gearbox) so if that earthing is meant to be occurring through the dynamo body, I'll clean it all up. I think I need to get it off and clean out the brushes as its not working yet anyway...

[Stuart Giles]

Unfortunately the regulator is a new electronic one that came with the car, so points sticking won't be an issue, I hope there isn't any issues with it as these electronics aren't exactly easily repairable given the biggest things on the circuit board is about the size of a grain of rice haha

The cut out relay is replaced by a power diode in all the electronic cutouts/regulators I've seen. the diode is there to allow current flow from the dynamo to the battery but deny current flow from the battery to the non charging dynamo when there is no charge. there is really only two failure modes for a diode: they either go from being a semiconductor to a being a straightforward conductor which will then allow reverse flow, or they just don't conduct at all i.e. they become a disconnect.

[12jslater]

Well now I'm confused, went to.the car today, ignition light comes on with ignition switch, start car and it goes out immediately just flickering at idle, however when I rev the engine the ignition lamp is now coming on and working in the exact opposite to.hoe it should, it gets brighter until about 2000-2500 rpm but no brighter???

[David Stepney]

If you had an electromechanical cutout, I would say probably dirty or burned cutout points, as the dynamo appears to be trying to charge the battery through the warning lamp. I don’t know much about electronic cutouts, but it sounds very much as if it is faulty.