Charging,?.

["Slack Alice" Simon]

With engine running, what does ammeter show?

If you then turn the lights on,which way does it move?

That direction should show you if the ammeter is connected correctly - or not.

[David.H]

Ammeter reads negative with ignition on and engine running then with lights on, furthther negative, which suggests to me that it is working.! The warning light stays on .
But the voltage atthe battery goes up a couple of volts with the engine running!
.............!
David

["Slack Alice" Simon]

Cut out not cutting in.

Is it working - you should see it move as you increase revs from idling.

If it moves, clean the points.

If it doesn't, check the connections to it, and continuity through its coils.

[David.H]

Thanks!
This is the diagram I have based it all on. I won't show my own "cat's cradle" diagram until I tidy it up.

["Slack Alice" Simon]

I'm afraid I frequently talk ... erm ... nonsense.  

My excuse is I only apply half a brain to the question,   the other half is on the garden,   whether I can get a bike ride in,   and whether the engine I have just put together is too tight to run, and why.   Amongst other things.

If you are getting that sort of voltage at the battery, then the cut out is closing and feeding the dynamo output to battery.

So why is it not showing on ammeter?

I will add that to the list.   If you have that sort of switch panel they can need a service - dismantling , cleaning contacts and checking the spring pressure on the moving contacts.

And the brass tracks can crack, which can be difficult to see.

The half brain bit is - whether any of that will cause the ammeter to show or not - I can't work out just yet.

Cheers

Simon

[David.H]

Simon
Thank you.
I am glad I am not alone out there! My problem is that I don't really understand electrics (as may be clear!) I have had the switch panel apart & back together...this may be the problem! I take your point about cracks in brass strips - or indeed in the body of the panel.
I have little doubt it will be something simple. I live in hope!
D

[John Cornforth]

Hi again David H

There is clearly something amiss somewhere.

I wondered if you would find it helpful to know how the charging is supposed to work on an A7 using the Lucas SM5 switch panel. Deep breath taken. The dynamo has an internal "summer charge" resistor from its main output (D or +) to its field winding (F or SHunt). If you start the engine and rev up, the dynamo will start producing a voltage. The dynamo main output is wired to the +D terminal of the SM5 and also daisy chained to the +D terminal of the cutout. Inside the cutout it goes through a fuse and is applied to the "voltage" coil, the other end of which is grounded. As the revs rise the dynamo voltage rises to the point where the (small) current through the voltage coil makes enough magnetic field to pull the cutout contacts closed. The cutout contacts then short from +D of the cutout (after the fuse) to A of the cutout. Current now flows to A of the switchboard, through its Ammeter and out of terminal B to the battery, and the battery is charged. A refinement inside the SM5 is an internal switch operated by cams from both the Left hand (Charge) switch and the Right hand (Lighting) switch. If either Full charge or Headlights are selected this internal swich shorts between D and SH on the SM5 with SH on the SM5 connected to SH or F on the dynamo. This effectively shorts out the dynamo's summer charge resistor and allows it to develop full whack.

As we have already discussed, the Ignition warning lamp is wired between +D and IGN on the SM5. Once the ignition is turned on, IGN is connected to A, so the lamp is effectively between +D and A. This places it across the cutout contacts. It will glow when they are open, and go out when they close.

All your descriptions seem to indicate that the cutout contacts are not closing. This could be because the cutout fuse is blown, the cutout voltage coil has gone open circuit, the earth connection is faulty or the points are very dirty. You should see some movement as the engine is revved up.

I don't know why you are seeing a rise in battery voltage when the ammeter is registering a discharge. Don't believe anything you read on a digital multimeter as they cannot cope with the fearsome electrical noise of a A7. Try and get an old fashioned analogue (needle) type voltmeter, even a cheapo one will do. Failing that wire a spare sidelight bulb directly across the battery and see if it gets brighter ( = more volts) when the engine runs.

The only way I can see that the battery could genuinely be charged without the ammeter registering would be if there was an incorrect connection somehow from the generator to the +B terminal of the switchboard. If you follow the car's wiring from the live side of the battery, there should be a connection to the starter motor and a connection to +B on the SM5. Nothing else.

Hope this might point you in the right direction

Cheers, John.

[David.H]

John
Thank you so much.....I will digest it...it does seem to make sense to me (!) Perhaps I should say I think I follow it. I can certainly put a bulb between the battery terminals if I cannot blag an analogue meter (if not I will befriend ebay). I used contact cleaning spray on the contact points,but will give them a mechanical clean as well. I am pretty sure my wiring follows the diagram. I do have additional wiring working the trafficators and the brake lights...and relays working the head lights/dipping.
I had not realised the switchboard was so clever!
Watch this space 
David

[David.H]

John C.....
OK this is the watched space!
All connections are correct (fingers crossed!)
Cut out fuse good. and continuity across it.
The points have been cleaned only one (?)
The engine started & revved...not movement of the points. The coil became warm and the insulation doesn't look great..The points did not close (& I didn't push them closed!)
I am not certain where to check the coil continuity but with the Battery switched off :-
There was continuity between the woven wire at the bottom of the cut out "hinge" up to the two "terminals on top of the unit. With the points open there was no continuity between the top "terminals" and the moveable cut out spring. With the points closed there was continuity.
Now this may be relevant or not: From D+ on cut out to D+ on switchboard :There is continuity - as there should be as they are connected! But there also appears to be continuity if I check between D+ and earth (Both at switchboard & cut out)
Make any sense?

[John Cornforth]

Hi David H.

Your measurement in-circuit of continuity from +D to ground is to be expected, it is simply the path back through the dynamo armature.

Those photos are useful. I think now that you have a Lucas CF3 cutout which incorporates an SB5 solenoid. This differs very slightly from the CF1 I had previously assumed in that the Fuse isn't in the main charging circuit but instead is used to supply auxiliary circuits. Austin didn't appear to use this feature, so the fuse does nothing and the bottom terminal in your photo (+ or +AUX) has no wire connected. Reading from the top, the terminals are A, Earth and +D

It is not impossible that there may be an internal fault in the cutout, for example a short circuit between the current (series) and voltage (shunt) coils, which are wound one on top of the other. Or the voltage winding, which has many turns of fine wire, may have gone open circuit. The outermost winding that you can see is the current coil, and the varnish doesn't look too good at one end. The heat generated in the cutout when it is running is pretty small but might be enough to detect by the "finger" test. I'd expect it to be warm but not hot after running a while.

If you want a more detailed description of how this particular unit works, take a look at: http://www.da7c.co.uk/History%20Section/...%20CF3.pdf Remember to halve the quoted voltages for a 6volt one, so pull-in should happen at between 6.85 and 7.15 volts.

To help diagnose any fault, it would be useful if you could do some resistance measurements of the cutout with it isolated from the rest of the wiring, by removing the wires to the +D and A terminals. The earth can be left in place. Here is what I would expect to see:

Points Open +D to Earth 60 ohms
Points Open +D to A Open Circuit
Points Open A to Earth Open Circuit
Points Pushed Closed +D to Earth 60 ohms
Points Pushed Closed +D to A Nearly Zero ohms
Points Pushed Closed A to Earth 60 ohms

The 60 ohms is just my guess at the winding resistance of the voltage coil. I don't know what test facilities you have, the problem with a simple continuity tester is that any resistance below its threshold will register as continuity and anything above as no continuity. It will still give some indication though, so give it a go.

Over to you.... Cheers, John C.