Morris Minor Owners Club

Hi, I would like some advise regarding dynamos, yes I know I should upgrade to an alternator with a kit however moneys a bit tight at the moment. Ive been told its the regulator that has stuck and as such should be replaced.I was also told you should replace the dynamo as well at the same time. Can you just change the regulator or do you have to replace the whole dynamo as well.The symptom is IGN light stays permently on. Any comments would be appreciated.

ANY part of the electrical system can be replaced on it's own. Replace the regulator or dynamo independantly or together it makes no difference.

If the light is staying on are you SURE it's not the dynamo? I had exactly the same thing and after replacing the regulator it turned out just to be worn brushes in the dynamo which cost £2.50 to fix!

You don't NEED to upgrade to an alternator. I have had lots of reliability problems with my alternators. Alternators charge the system better (they charge at low revs where the dynamo doesn't) also they produce more charge than the dynamo, BUT generally speaking, the dynamo is more reliable. I have an alternator on one car and dynamos on the rest.

Thank You Cam,

Im not sure what to do now, Were on the L2B on Sunday and I need to order parts 2morrow to be sorted for the weekend.

Pity you don't have another dynamo to try out. If I were closer I'd come and give you a hand. I'm hopefully on the L2B on Sunday too!

I think the best thing is to just plump 4 a new regulator and dynamo, I must admit I feel happier knowing that a new alternator is not always the best option.

see my PM I might be able to help - Roger

Hi
It might be worth double checking the wire connections. I had the same problem, it turned out to be the connector to one of the terminals that had become detached. Didn't even cost £2.50 to fix!

Thanks Dominic,

I did check them yesterday, however I will double check again before spend any cash.

Paul - I'm in Bedford do you want a hand testing with my multimeter

I don't know why my private message hasn't arrived they sometimes take a while.

Thanks Roger, have sent another PM

Why do you think the regulator has 'stuck' ? This would be unusual. I would check the brushes first - easy to do, and i assume the fan bet is snug? Last alternator I bought was £1 at autojumble - still running fine in the car. Alternator replaces both regulator and dynamo - so will be less expensive. So saying dynamo I got last year was also £1 - and it had just had new brushes fitted. Best to get these things 'in stock' when the price is right.

Hooray for RogerRust

Roger's been around, New regulator and Dynamo on order ASAP. Many Thanks for your help Roger. It would appear there's no charge to the battery from the Dynamo and with further inspection the right side coil on the regulator, the contact sticks.Would be intrested to know if this is normal. In the meantime need to get this fixed before Sunday.

Not quite sure offhand which one but yes, if you close one of the regulator
contacts by hand with the engine OFF then it will not release again without
a great deal of effort and, if you do this, the dynamo is acting as a motor and
is trying to turn the fan belt! It would quickly burn out so don't persist if that
is what you are doing. Does your windscreen wiper still work? I ask because
it uses the same earth as the control box so if it is not working that would mean that the control box was missing an earth too.( a black wire goes from
terminal 'E' into the wiring loom and emerges about six inches lower down
behind the loom and is earthed under a bolt head). Make sure it is a good contact.

Thanks for that, I will check 2morrow when its light. Since the problem started have disconected battery until I fix it.

Paul, if the dynamo is not charging properly or intermittantly contacting (in the case of worn brushes) then the contact will keep trying to 'cut out'. You can flick it back into place and the light will go out but soon after it will flick back and the lamp comes back on. These are the symptoms of worn brushes in the dynamo, but unless you strip it down or make some electrical tests then it's pretty much guesswork. On the positive side (no pun intended) a new dynamo & regulator box will cure it!

If I were you though, I'd fit the dynamo first and test things. Then if all is fine you could return the regulator unused.

We found two problems on inspection;

1) I disconnected both the D and F at the dynamo made a temporary conection between the terminals and started the engine. Result 0.9 volts only. This is with the dynamo self exciting and Haynes suggests an expected voltage of 15 Volts. O volts would be a problem with the brushes. 1 volt indicates that the field windings are probably suspect.

So the Dynamo is shot - shame because it looks quite new.

2) Even with the dynamo disconected the red ignition light stays on when the engine is turned off. On inspection the cut out relay in the voltage regulator is staying energised and only releases when the battery is disconnected.
I cleaned the contacts carefully but no change.

At first I wondered if the ignition switch was faulty, but the engine stops when you turn off. So I suspect its the Control Box.

Do you think the cut out problem has resulted in burning out the feld windings?
I'm OK with dynamos but not so sure with Control Boxes. In my experience they may very ocaisonally need adjusting but don't often fail.

Any thoughts guys or girls.

As a precaution I reminded Paul to polarise the new dynamo before starting the engine.

http://www.morrisminoroc.co.uk/index.ph ... ic&t=10041
But in this case its the polarity of the dynamo thats being fixed and not the battery thats eing changed round.

Have you taken the dynamo apart and looked at the brushes yet?

Why isn't this posting in the electrical section?????

newagetraveller wrote:Why isn't this posting in the electrical section?????

*cough*, erm yes, good point. Moved to Electrical...

Did you see when all was connected if the 'F' terminal had 12v on it? and if so what the corresponding 'D' voltage was? Probably not given your description. It does sound very much like the cut-out is stuck 'cut-in' as you say with the lamp being lit all the time with the engine off.

Well, a new reg & dynamo will cure it!

I'd still like to put 12v to the 'F' terminal and measure what the 'D' terminal was producing, just out of interest...