Morris Minor Owners Club

The ignition light on my 69 Minor goes out when the engine starts but sometimes flickers on as the engine revs increase. It flickers as it should when the engine is idling.
I thought that the fault would lie either in the Dynamo or the Control Box.
The belt does not appear to be slipping.
I thought I would check the voltage output of the Dynamo first to see if for some reason it was falling as the engine revs increased. However when I went to disconnect the leads from the Dynamo I noticed that the thicker ( black and yellow lead?) that is connected to the lower terminal is very brittle and has started to crack at a section where the wire has been bent to meet the terminal. I have temporarily wrapped it in insulation tape and the engine starts as normal. The wiring loom appears to be the original.
Would the best solution be to join a new section of wire onto the end of the brittle section to take the strain off the wire OR to run a replacement wire from the Dynamo terminal to the Control Box terminal…..I believe this is where the large wire leads.
Also once I have sorted out this issue would it be possible / easier to take a Dynamo voltage reading off this wire at theControl Box end rather than fiddling about between the Dynamo and the Distributor Cap?
Any advice would be gratefully received.

Mike
Thanks for your reply. Yes it is the plastic sheathing that I mean. I have been slowly working on the car for a while and while generally the wiring is all pretty grubby this is the first bit that has actually cracked when I tried to move it. All other electrical items seem to be working fine.
I have seen the replacement looms on various sites and might well try to replace it over the winter. Being partially colour blind makes these sort of jobs a bit more problematic.
It is just that to date I have not had it out on the road in earnest. I think that it is just about up together now and I wanted to get it insured and “ unSORNed” and out on the road in the next few week.

I have seen the replacement looms on various sites and might well try to replace it over the winter. Being partially colour blind makes these sort of jobs a bit more problematic.

I have seen a few people on here mention they have this issue in the past, so you are not alone.
Contact your local branch, once you have a replacement loom someone will doubtless be happy to pop round and give you a hand.
One thing, when buying, make sure you get the correct loom for your year of car.
Also advise the company you buy from if you have things like an alternator fitted.
There were variations to the looms over the years.
Best wishes,
Mike.

I'd second the replacement of the wire immediately ( regardless of whether you go down the loom replacement route ).Before buying consider adding " new " stuff to the loom e.g rear fog light , hazard lights , etc. subject to
your personal wish list. It will cost a little extra but the car wiring will look neater without loads of extra added on stray wiring.
Dynamo testing... a good explanatory video by Moss ; -
https://www.youtube.com/watch?v=RjLW_eb3D-c

2 wires on the dynamo Brown / Yellow ( Ignition warning light ) goes to the D terminal on the Control Box
Brown / Green ( Dynamo Main supply ) goes to the F terminal on the Control Box
Your car's wiring , probably 53 years old now , might well have turned your Brown colour element to Black
by now !! I too am partially colour blind , red / green , so can sympathise with your identification. An " assistant "
always comes in handy.
I source my wiring stuff from Auto Electrical Supplies Ltd , have done for years. Other suppliers are available.
Select your colour choice from the drop down , against your wire size listing.
https://www.autoelectricsupplies.co.uk/product/66
Select an appropriate size Female Lucar connectors from the list
https://www.autoelectricsupplies.co.uk/ ... category/2
Plus most importantly insulation sleeves to keep the connections clean and waterproof
https://www.autoelectricsupplies.co.uk/product/2
DON'T forget to slip the insulators on , before you crimp on the Lucar connectors to the new wire !
Cable tie wires together / or to convenient points ,so that nothing will catch against moving parts.

If the dynamo tests as being a bit suspect... before panicking...having disconnected battery , removed from car
check out the state of brushes. A new set of those and a general clean up might give you several more years
of service. Who Knows. If you might replace a truly duff dynamo with an Alternator, then this would be one of
your " alterations " to a future wiring loom replacement.
It's all in the planning , getting it going well and keeping it that way !
Good luck Bob

Andyhereford wrote: ↑Sun Feb 06, 2022 3:26 pm Being partially colour blind makes these sort of jobs a bit more problematic.

Hi
Yes, that's evident from your description, although, I must admit the colours can be difficult with the age of the wiring.
On the earlier Wiring Diagrams, the Dynamo output is listed only as Yellow, on latter diagrams it's Brown/Yellow.
That basically conforms to British Standards BS-AU7 as it changed over the decades.
So as you're saying its a Duo colour, Brown with Yellow, that's right for your car being mid-late 60s.

There's no reason you couldn't do the rewire.
Basically you would need to get the right loom for the car and then lay it out somewhere.
Then identify the individual legs of the loom, going the Behind Dash, headlamp/sidelight etc.
Either working with someone else, or checking each line through with a multimeter, put a number on each tail as it comes out of the loom, corresponding to what it is.
Essentially putting the number on it that the Wiring Diagram says it is, so you can refer to the diagram when installing.

Thanks to you all for your replies. This really is an excellent and very supportive website.
Excellent YouTube Bob on how to test the Dynamo.
My intention will be to replace the two wires as soon as possible ( there is an auto electricians in Hereford where I can get the correct grade of wire etc) as a short term fix and then in the winter have a think about replacing the wiring loom.
It will be a good exercise in learning about the various parts of the car!
Thanks again for all your help.
Andy

Thanks Andy. The Forum always appreciates feedback on help / suggestions / advice.
Keep the questions coming it exercises our " little grey cells ".
Bob