Chasing errant current flow with a meter on amps it is easy to destroy the meter. Interpreation of volts requires some thought. Similalry, unless the battery is isolated, use of the resistance range on a meter can lead to ruin of the meter. For old style car work with no electronics a bulb with leads is very useful. Can connect in series with the battery and disconnect items until flow ceases, without a damaging current.
Beware the cutout does not become operated and locked. If prodded when dyn not working must pull apart or disconnect battery to release.

Location: Auckland, NZ

If you put a meter in across the battery and +feed to the car, what are you doing exactly?

A volt meter across the battery +6V and -0V will read 7V or so.

A volt meter across the battery -0V and the "B" or "A" terminal of the switch panel will read 7V or so (irrespective of switch position).

Terminal "A" is also connected to the cut out. If the contacts of the cut out are closed, then current will flow into "D+" of the dynamo. But this should not be a short circuit but you will be heating the dynamo.

If both switches are in the OFF position and the cut out is open, then no current should pass as the other terminals on the back of the switch panel are not live.

Is there a large discharge registered on the ammeter?

- No? the short is occurring on the way to the switch panel (perhaps the "B" terminal is shorted to the dashboard?)

- Yes? the short is occurring after the ammeter, but before lights, coil, horn (perhaps the A terminal is shorted to the dashboard or cut out is short).

Hope this helps

Peter


ETA - following from a previous post - another failure is that the split pin that holds the switch knobs on can short against the face of the switch panel (but usually only when the switch panel is screwed in to the dashboard).

Hi Peter
Wow - thank you for all this knowledge. I will check these things tonight/tomorrow and let you know how things stack-up
regards
Adam

Location: london

Hi Adam,

I'm a long term Mac user and have no problem posting photos to this site. You need to follow the instructions described in the second topic down on the index page - "Posting photos on the Forum".

I upload photos from my Mac to my Photobucket album then choosing 'SHARE' copy & paste the image link onto this site remembering to change both IMG caps to lower case img and deleting [/URL]

Jeff.

Location: Almost but not quite, the far North East of England

Hi Jeff
I think this works...


http://s1249.photobucket.com/user/AdamCRWhite/slideshow/


Thanks!
Adam

Location: london

Thank you Bob
I am planning to work my way through the advice and guides today so will post results later
regards
Adam

http://s1249.photobucket.com/user/AdamCRWhite/slideshow/

Location: london

Hi Peter - results just in...

..Battery + to Battery - (should be around 7 volts) - yes
..Battery + to "A" on switch panel (should be zero) - yes
..Battery - to "A" on switch panel (should be around 7 volts) - yes

All wires added sequentially back and two things found: First was a short at 'A' to the horn - this was because I have used the early horn push button to earth rather than the inline switch on the circuit diagram ( 1929, Handbook 619C) so will sort out by isolating the horn and taking the power feed via the horn and then using the horn button to earth/complete the circuit)

Second short is at the 'A' terminal, when connected to the Cut-out.

Before connecting, the A terminal does not register when tested as you describe above. When connected, I get a full 6.5 volts between 'A' and the battery +

Does this mean there is a short in the cut-out? It is old, but all looks in order and the contacts are undamaged and open with a gap of 30/40 thou

I have uploaded pictures to link below:

http://s1249.photobucket.com/user/AdamCRWhite/slideshow/

As ever, thank you very much for your advice,
Adam

Location: london

Hi Adam,

Looking at your photo of the switch plate and the cutout, your black wire both terminate at +D at each end but your green and purple goes from A on the cutout to B the battery terminal on the switch plate so logically you have the feed wire from the battery to the A terminal on the switch plate. it that so ??

Hi Paul

Answers to your questions below:


Looking at your photo of the switch plate and the cutout, your black wire both terminate at +D at each end

Correct - the black wire is continuous from switchplate connector to cutout +D

but your green and purple goes from A on the cutout to B the battery terminal on the switch plate so logically you have the feed wire from the battery to the A terminal on the switch plate. it that so ?? [/quote]

It appears so from the photo's but the switchplate was wired some time ago and I didn't follow the colour coding when routing wires through to behind the bulkhead so: The green/purple from the cut-out goes to the 'A' connection on the switchplate, the +B connection to the battery positive

Thanks
Adam

Location: london

The horn button wiring should be on the earth side of the horn. The 1929 horn button just doesn't work as a switch, it can only work with a single connector. I know, I tried for ages to get it to work.
The wiring diagram in the handbook shows it incorrectly. The one in Bill Williams 'Austin Seven Specials page 122 shows it correctly.

You can see clearly on Adam's photo of the back of switchplate that it is marked A at the left hand terminal and B at the right hand terminal and the lead from A on the cutout goes to B on the right hand of the switchplate.

Hi Peter, All

I think I have cracked it.

Just checked over the cut-out and all seemed OK, so went back to look at my wiring and quel surprise - driver error!

The original problem was the incorrect wiring of the horn, causing a short from the 'A' terminal, and as I disconnected and checked things, I mixed up my identically coloured wires from cut-out and Dynamo - and added that as a secondary problem - now identified and corrected. Manic tidying into sleeving and not enough colour coded wiring to choose from was my undoing.

So now everything is wired up and responds correctly to the switches - including the hooter!

Will have to wait until tomorrow for the running test to see whether the old girl is charging, which hopefully won't lead to another chapter.

Thanks again to all contributors - a problem shared is a problem halved.

Adam

Location: london

Adam, to eliminate same coloured wiring mistakes,cut a 1/4" of shrink sleeve and put on the ends of your similar coloured wires using the sleeve colour as the trace. I recall Citroen using all green wires with trace sleeves on the ends.

Location: Piddle Valley

Adam

Pleased to hear of your success! Charging can be another problem altogether. Luckily with modern LED lamps, the problem now is an excess of charge!

Peter