Morris Minor Owners Club

Hello everyone , After fitting a new dynamo to my 1956 convertible the ignition light stayed on for around 5 minutes before going out , today it wouldn't go out at all Any ideas as to what the problem could be , she starts and runs fine ..new dynamo has been in about 3 weeks. Many thanks, Liz

Liz,

If the old dynamo did not cause this problem (and still does not) then either the fanbelt is slipping, the dynamo has not been polarized correctly to your polarity (either positive earth or negative earth), you have a faulty wiring system, your regulator is a bit dodgy, or your new dynamo is a bit duff.

Check your polarity (see which battery terminal is connected to the body) if it is negative (-) then instructions for re-polarising your dynamo can be found in the technical tips section of this website.

If it is positive, I would recommend that you swap over to your old unit and see if the light still stays on, if so it sounds like a wiring / regulator problem, if not a dynamo fault.

If you have a Haynes manual then have a look in the electrical section, it details problems and possible causes.

If you haven't got a Haynes manual, there is a couple on eBay at the moment for a few quid.

Many thanks Cam, Rod had a look at it today and it certainly looks as if it's the regulator thats at fault, he is going to take one off of one of the others to try it tomorrow to see if it is that. I have got the Haynes manual so will have a look at that. Many thanks for all your advice I will let you know how we get on. thanks again Liz

Well Rod has been looking and checking all day and we still don't know whats causing it. He seems to think it may be something to do with the wiring and has checked all except the immobilisor..question : would the immobilisor prevent us from correctly polarising the dynamo Rod has put a regulator from another 56 model and the light still stays on any help much appreciated

You don't say why the dynamo was changed in the first place. Was it charging poorly (the ignition light glowed dimly)?

The immobiliser shouldn't have an influence on polarity. However I believe polarity may be the key. I converted my Minor to negative earth when I installed a Clifford Immobiliser. I checked and the manufacturer stated it wouldn't work on the original (positive) earth. I guess therefore that your car is also negative earth. In which case you will probably need to correctly polarise the new dynamo before it will charge the system (as Cam thought). Has this been done? And if it's not charging the system (due to incorrect polarity?) then the ignition light will glow bright red. Remember that the Haynes manual assumes the car is positive earth, as built.

Whatever the reason, your car will still run as long as there is enough charge in the battery left to create a spark. I wouldn't advise any long runs though.

hi chris thanks for info just spent all day checking all the wiring changing
regulator etc.and still the light stays on i,ve just had another look at the hayes manual which i followed to the letter and there it is quote----note.. replace the negative lead before the earth[positive] lead
bearing in mind the car is negative earth i think i,ve got it? :
thanks again i,ll confirm success in a day or two
regards rod, dogsbody,greasemonkey,mechanic etc. for mabelminor

hello all
Well it turned out it was the new dynamo only giving out 6 volts so it's back to the shop with that at the weekend. took the dynamo from the 56' traveller and the problem solved Thankyou very much for all the excellent advice liz xx