Morris Minor Owners Club

Hello
Coming home from work this afternoon my ignition light came on and stayed. I got some new brushes for the dynamo and fitted them.
The light is still on.
It is bright and will go out when revved in neutral and during driving it will go out in 2nd at about 30!
Any ideas , could it be a new fan belt needed , is it likely to be the control box.

mark

The check for the fan belt tightness is to see if you can easily
turn it by hand, it should JUST be possible to move it against
the drag of the belt. If it is easy to turn then you need to
adjust the tension. The voltage regulators are usually very
reliable so it is more likely to be a faulty dynamo. Were the
old brushes worn out(sooty black on the surface which contacts
the commutator)?

Hi
The brushes had worn at angle, one edge down to about 1/8 inch the other about 1/2 inch. There was a bit of play in the bush the commutator end.
Mark

strange, with the correct size brushes they should not be able to
tip over enough to wear at that angle! They are of a fail safe
design so that when they are well worn the brush spring rests
on the brush housing and doesn't cause any damage. strictly
speaking, the commutator should be 'undercut' which involves
using a hacksaw blade to remove some of the insulation between
the copper segments on the commutator. each of these segments
is wired internally to another. In other words, it is probably a
good deal easier to buy an exchange recon dynamo with its
guarantee than to try it yourself? So if you have checked
that the two leads are still on the terminals at the rear of the
unit and the fan belt is tight enough you can either get another
dynamo of get an auto electrician to check the output.
The play in the plain bush would have to be chronic to allow
anything other than the brushes to hit the commutator....you
would have noticed any damage. It is awkward to remove
that plain bush...another reason to exchange the dynamo?