Charging,?.

[Bob Culver]

Without reading this all thru yet again, a 6v cutout, as per John cornforths excellent circuit diagram, is 30 ohms. The one in photo looks very cooked. Some enamel wire was black but usually dark red brown.

[David.H]

I have a simple digital multimeter, but can get an elderly decent analogue one.I will have a go as you suggest tomorrow and see what numbers I get.
The car is an AG steel body,short chassis from 1932. It was altered in the 60s to have hydraulic brakes,S 4 speed box, Nippy manifolds & downdraft Carb.and Ruby wheels. It went out to Hong Kong with a British Policeman who sold it to an American and it went to California And on to Ohio where it broke a half shaft and languished in a shed for 30 plus years! It was awful!
So what happened to the electrics goodness knows.  I have totally rewired it And this is the last glitch!
Thanks so much
D

[David.H]

John C
My multimeter didn't like going below 200, so the readings may be off as you suggested
From the top
~40ohms
No reading/nor continuity
no reading/ nor continuity
~60
~20 (maybe!)
~60
Any comment?
I will have an analogue meter next week that should go low enough!
Meanwhile I will continue with the trim............!

[John Cornforth]

Hi David H

Allowing for the vagaries of your multimeter, those figures look mostly OK.

However, the resistance from +D to A with points closed should be VERY low, (a fraction of an ohm ) as it is just the resistance of the closed points plus the thick "current" (series) coil. This sort of resistance is hard to measure accurately with a normal multimeter. One check is to short together the probe tips of your meter (push hard for a good contact) and see what it reads. If you don't get almost the same reading when you try it on the cutout, that would raise suspicion.

I find that when measuring the generally low resistances of car circuits it is often necessary to use sharp meter probe tips and to really push hard/scrape/wriggle to get a good enough contact, as the metal surfaces build up a film of poorly-conductive oxide. Measuring voltage is less critical, as the meter's own resistance is so high that a bit of extra probe resistance doesn't affect the reading nearly so much.

Happy trimming !

[David.H]

John C
Trimming done!
Had another go at taking readings that looked pretty close to your suggested probable. 
SO, back to real basics. I had a very close look at the dynamo terminals and one (larger dia) has a tiny letter D the other has an F. The wires coming out of the dynamo are slightly different thicknesses and the slightly thicker wire from D goes to the SH (and on to the cut out) and F goes to D+ on the switch board  
I have a nasty feeling these should be reversed.......! Is F(ield) the same as SHunt? -  and D the same as D(ynamo+) ??..........
As an aside,  where the wires come out of the casing the "insulation" is totally carbonised and the wires look a bit tired, but use able.  I will try & put a grommet of some sort  to stop them chafing.
I hope nothing has cooked!
David

[John Cornforth]

Hi David H

Its funny you should say that, but the other day when the dog woke me up at 5 AM to bark at the pigeons I started musing about this charging puzzle.  I wondered whether the Dynamo and Field connections had been inadvertently swapped at some stage.

The stamped markings on the dynamo case aren't 100% reliable, as the phantom bodger may have dismantled and reassembled wrongly.  However, you should have:

Dynamo Thin wire = Field (F) = Shunt (SH)   is the field winding with a small terminal
Dynamo Thick Wire = Dynamo (D or +D)      is the main charging output from the dynamo with a large terminal

When I say thin or thick I am of course referring to the wire diameter inside the insulation.

I suggest you carefullly remove the wires from the dynamo terminals, check their diameters and slide some fresh insulation over the last inch or so (where they go through the hole in the case) before refitting.

Regards,  John Cornforth

[David.H]

John,thanks so much for your advice. ......our pair of lurchers also shout at the early birds! 
I will try this morning . The dynamo wires are quite short and have U shaped slide on connectors which I will try and replace with ring type and re solder. While doing that I can shrink wrap them all and make up a grommet if I can. It will be fiddley job without taking the dynamo off. More backache.
I will test it first before redoing all the terminals. 
Watch this space.
D

[David.H]

Good news and bad news!
Started up & to start with light stayed on, but was brighter on summer charge. Then it went out & registered a healthy charge. Then it went on again! Did this a few times while holding steady revs. Then it stayed on! So at least the connections are now right!
Voltage at Battery ~ 6v.So nothing getting there.
Then I noticed the fuel leak! So I will remake the joints from the tank (and fit the in line bowl filter) . I am running out of my stock of early pipe fittings so may have to compromise & use some clips!!

["Slack Alice" Simon]

Use a low grade ( ie. not stud or bearing fit) loctite as a sealant on fuel line joints.

It usually fixes minor leaks and because it is the weak grade, doesn't make things difficult to undo.

[David.H]

Thanks for that tip