Morris Minor Owners Club

Hi would appreciate some help, my ignition light on all the time, read up and search this forum, on the back of this I checked the fan belt all good, broken dodgy connections nothing obvious, checked the battery with multi meter and showing 12.6 volts, checked the battery whilst the car running and found no increase in voltage.did the check on the Dynamo wiring the terminals together then connecting to the non earth terminal on battery nice spark but no life in the Dynamo!is is just a case of replacing the Dynamo or can I repair as a novice?, also would a non operating Dynamo make the car idle rough?

Many thanks in advance

Assuming that when you say "no life in the Dynamo" you mean it is not generating, then it could be worn brushes, which you can replace faily easily. The rough idling may be due to something else, although if your battery is very low and no charge, the engine will start to falter and stop as there is not enough voltage to create a good spark.
Quick dynamo test - remove fan belt, remove cover of control box and press down the cut-out contact (the one on the right hand side as you face the car...do not press the regulator contact). A good dynamo will then run briskly as a motor. Make sure the cut-out disconnects again after this test.

Hi I did the test described on here where you connect both Dynamo terminals to the non earth battery connection, this should make the Dynamo run as a motor, but nothing happened?i have the battery and Dynamo off the car now is there another simple test!, I took the Dynamo apart it looks pretty old in side, and I can see how the bushes are fitted.how do you know when they are worn, they do look pretty sad!

Can see how why this would stop working all the wires are connected, I understand the bushes could run out, but they are still touching?

Did you have the fan belt off/loose when you did the test? The dynamo can't run if the belt is still taut on the pulley - but it should 'twitch' as it trys to run. If the dynamo is out of the car now and you have a good battery, join the terminals together again, secure it in a vice or with your foot, connect the end plate of the dynamo to earth and then connect a wire to the joined dynamo terminals. If it will not run as a motor then it is goosed.
Compare the brushes to these new ones: https://www.morrisminorspares.com/elect ... 41-p829715
Dynamos can fail because of other reasons than worn brushes though......

Ok thanks yes I disconnected the belt whilst in the car, when you say earth the end plate, how do I do that run a cable touching the body of the Dynamo and touch it to what the ground? Then connect the two terminals to the non earth side of the battery

So, if you have a +ive earth car (which I assume as you have a dynamo) the two joined dynamo terminals are connected to the -ive post of the battery and the dynamo body is connected to the +ive post of the battery. It should then motor briskly..

Ok brilliant I understand, it’s negative earth so as you said but the other way round, two terminals of synopsis to the positive and the body of the Dynamo to the negative earth terminal

Yes, that's it if your dynamo has been polarised to be -ive earth.

Ok brilliant I understand, it’s negative earth so as you said but the other way round, two terminals of synopsis to the positive and the body of the Dynamo to the negative earth terminal

Did the test and it ran well, so what now the control box?

Although this test didn’t work when the battery was inaugurated?

I meant insitue

Well, if it ran as a motor when out of the car but not 'in situ' there could be a wiring fault/poor connection in the car. Put the dynamo back in (but don't fit the fan belt) and test again - don't connect the F and D wires from the control box to the dynamo, but connect the two dynamo terminals together and connect these to the non-earth battery post. The dynamo will earth via being bolted to the engine.

Try stripping it down first and check the brushes, the springs holding them onto the commuter may have rusted away and they are not making contact with the commuter. If the brushes have worn away replacements are available.
A cheap and easy repair.

Hi yes that what I gonna do had it in parts and all seems reasonable, probably worth changing the brushes whilst apart, cant believe how simple it is.it is rather dirty in side thought could spray with wd40 and give a good clean before reassembly. Just need to try to understand the control box functions so been reading up, thanks for all advice much welcome

I'd leave the WD 40 on the bench myself. It's very useful for a lot of things. However it is a bit "sticky" after
use.It will therefore attract more dust from the carbon brushes and after a while you'll be back where you started.
You want to keep the old varnish on the windings dry. Any penetrant spray , carb cleaner, white spirit, etc is likely
to damage / affect the varnish. ( Think replacement dynamo if you're too gung ho )
On the same theme use sandpaper for cleaning up the commutator NOT Emery paper or wet and dry paper.
These both usually contain carborundom in the grit. Carborundom ,is a conductor and the grit can bed into the
separators , between the segments and short them out.
A gentle brush ( an old tooth brush ) dry will get rid of most of the dirt. A cloth or paper towel, lightly dampened with Meths or petrol can be used for the final clean up of the commutator.
Bob

Changed brushes etc on Dynamo, ran ok out of car, put back started car, but ignition light still stays on, the control box doesn’t seem to be cutting out or the regulator isn’t buzzing? Check the the Dynamo voltage whilst car running only 1 volt, also the regulator box sparks even when the ignition turned off, is that right?tested the wiring with a multi meter seems ok?

Can you give us a bit more detail?
How and where did you check the dynamo output?
Where is the voltage regulator sparking with the ignition off?

Hi, I ran the car and held the red lead to the D terminal on the Dynamo and the the black to the battery negative earth, and it showed only 0.99 volts output. Whilst fiddling about I noticed
That when I put a metal file between the points on the cut out it sparked even though the ignition was off? I didn’t think there would be any power to the control box with the ignition off?