Welcome to the Austin Seven Friends web site and forum

As announced earlier, this forum with it's respective web address will go offline within the next days!
Please follow the link to our new forum

http://www.austinsevenfriends.co.uk/forum

and make sure, you readjust your link button to the new address!

Welcome Austin seven Friends
This Forum is Locked
Author
Comment
View Entire Thread
Re: RN not charging

No charge is a recurrent theme with Sevens. Dig around with the Search facility and the various Club site electrical articles and see where you go from there.
The basic test is to isolate the dynamo, connect field and output together and momentarily measure volts to earth. Should considerably exceed 6v at modest revs. Brushes can be examined with a lamp and mirror.
I have various analogue meters but for old style car work using digital I suspect a thousand or several ohm resistor and/or a small capacitor across the meter terminals will eliminate the radiated interference from the ignition system. Someone may advise more positively.

Location: Auckland, NZ

Re: RN not charging

Is the ignition warning light bulb OK, and It's not 6 volt, I think 3.2 volts from memory. Alternatively there is a resistor wound round the bulb holder that suffers from a broken connection I've used a 27 ohmn resistor from Maplins to resolve this. I've found that the dynamos benefit from an operational ignition warning light to self excite after a period of inactivity.

Re: RN not charging

I had no ign warning light bulb in my RK when I got it, so ...knowing nothing... I put in a 12v 2.2 (from a TR3A instrument panel!) and , as I hoped, it glowed well enough (and goes out as it should). My AG also is without a bulb, but the technique above (I have several left over TR bulbs!) hasn't worked even though the ammeter shows a discharge when the ign is switched on. It has a rather dodgy looking bulb holder, although it reads 76v at the centre pip.
I haven't yet got to the stage of finding out if the dynamo charges; I am happy enough that the starter works!
David

Re: RN not charging

The ignition light doesn't work, but when I switch the lights on shows a 10amp disharge. No difference if summer or winter charging selected. I've ordered an analogue volt meter and will start with the dynamo and work backwards.

Location: Scarborough

Re: RN not charging

Ok, so we know the ammeter is working.

Take the cover off the cut-out.

When you rev the engine, does the cut out move at all?

If not....search this forum as to things you can do to fix/check the cut out.

Simon

Location: On a hill in Wiltshire

Re: RN not charging

Apologies, I tend to be a bit short on details.

If the cut out isn't closing, your dynamo could be working fine, but you won't know.

Sometimes, it just sticks, due to old age. If you find it isn't moving when you rev the engine, switch off and see if it is stuck open. Maybe you can free it off - if so, start the engine, rev and see if it closes.
If it does, you may then have a charge showing on the ammeter, problem starting to be solved.
If it is free and doesn't close - then you go on to see if the dynamo is giving an output, using your new analogue voltmeter.

Simon

Location: On a hill in Wiltshire

Re: RN not charging

For car work much can be achieved with a simple test bulb.

For pre electronic cars the most cheap and simple analogue meters suffice. It is not then a disaster if accidentally burn out on the amps or ohms range. As we are not adjusting voltage regulators, accuracy is of little consequence. (Can be calibrated against more accurate digital).
The important thing with a Seven is that the dynamo field and output are not electrically connected (anywhere) and to nothing else (except briefly). Normally, once charging, the dynamo is connected to the battery and volts do not soar above.

(For cars which have acquired the 1930ish later 4 pole DEL dynamo the internal field resistor may still be intact, so disconnecting the external connections does not isolate the field. If the dynamo has to be disconnected from the system then, contrary to normal electrical practice, a full earth applied to the isolated output assures no damaging voltage is developed. The 4 pole dynamos have 4 countersunk screws disposed around the body and main brushes at 90 deg)

If fiddling with the cutout and the dynamo is not charging, it must not be operated and left that way. Either pull open or disconnect battery.

Location: Auckland, NZ

Re: RN not charging

Any dynamo faults I encounter usually end up with the dynamo clamped in a vice and I use an electric drill to drive it using a piece of 1/2" square bar with one end turned to 1/2" diameter to fit the drill and the appropriate socket on the square to drive the dynamo. The dynamo D & F terminals are linked and the voltmeter now well away from interference from the engine ignition system is connected to the D terminal and the dynamo case. If the dynamo is any good You have to grip the drill firmly or it's on the floor and you will get between 18 and 24 volts at 2400 RPM.

Re: RN not charging

Jez Benson
I have recently come into ownership of a 1932 RN. The ammeter does not show a charge when the engine is running. I have a voltmeter and the batery shows 6.32 volts. When I start the car the voltmeter goes mad. It registers anywhere between 15 and 19 volts, sometimes a minus discharge, but the reading changes so fast you cant really see the reading. That was engine running, voltmeter on battery. The same thing happens when I connected it to the cut out, and also the dynamo. The ignition charging light remains off at all times.
Any help to point me in the right direction would be appreciated.
Jez.



Right - I have an analogue voltmeter. The battery shows 6.4 volts when engine not running, drops when the starter works, then returns to 6.4 when engine running. Ammeter shows -2 when all disconnected, a steady -8 when the engine is running. No fluctuation. The ignition light remains off whatever is happening. No difference in charge switching to summer/winter, Goes past the - scale when lights turned on. My car has an SB5 Cut out, and when the engine is running and I connect terminal A and D the meter shows 6 volt charge. Drops and goes erratic when engine idling. I have a Lucas C35A dynamo. When I connect the two terminals I get a 1 amp reading. The cut out does not appear to move and connect. On the dynam which terminal has the red blob, and which is the blue one?
Electrics not my best subject. Help would be appreciated.

Re: RN not charging

Sorry Jeremy, I cannot fathom your post. Are the readings all discharges?
Analogue meters can be quite inaccurate but a true 6.4 volt implies battery is reasonably charged somehow.

If dynamo not working ammeter should not significantly alter after engine starts.

As with other similar enquiries suggest you peruse the introductory articles on Club websites, and many old posts about not charging. And final understanding will most likely be better assisted by the Cornforth circuit diagram (typical) rather than from Austin wiring diagrams.

Assuming all as original the red terminal is the output D (early cars were -ve earth)

Location: Auckland, NZ

Re: RN not charging

Watch out for digital meters and differing polarities (they don't like being upset by large currents going in the wrong direction). Across the battery will give you a voltage (engine off) reading but if the charge is going into the meter back to front then those little diodes inside your precious little meter are going to get swamped by excess current and questionable polarity!

Re: RN not charging

The SB5 is the relay/contactor model number which was fitted to the CF3 cut out which had 4 terminals and 1 fuse and the CFR cut out which had 6 terminals and 2 fuses amongst others. Originally the RN was fitted with the C35A dynamo which had a box on it's top housing the field resistor, field fuse and the 2 dynamo terminals connected to a CF3 cut out. The dynamo terminal nearest the engine is the D terminal which should be connected to the SM5 switch panel D terminal. The other, furthest from the engine, is the F terminal which should be connected to the SM5 switch panel SH terminal. The A and D terminals on the SM5 switch panel are connected to the CF3 cut out A and D terminals respectively. For the cut out to work it must be earthed at it's E terminal. One of the reasons for dynamo poor performance is poor connections in the dynamo terminal box and SM5 switch panel. To save your knuckles remove the fan belt while testing the dynamo in place.
You say " I connect terminal A and D the meter shows 6 volt charge" would suggest the dynamo is doing it's stuff, but not charging.
You go on to say "When I connect the two terminals I get a 1 amp reading. The cut out does not appear to move and connect The cut out does not appear to move and connect" Where are you getting the 1 amp reading, most basic meters will not handle anything more than a few milliamps?

Re: RN not charging

Think it's the brushes. Worn down and commutator filthy. The brushes I've seen are just carbon pieces, whereas mine have a short lead and a shoe. Also I could do with 3 pole shoe screws. Could someone point me in the right direction please. Ta Jez.

Re: RN not charging

Brushes etc are available from our cherished suppliers. Click on the Austin Logo at the top of the page and then "cherished suppliers" and scroll down for info.