Hello, After a winter in a Swedish barn my woman's Moggy is out on the Swedish roads again. Day one: some serious misfireing. Day two: New dizzy cap, rotor etc took care of that problem. Today we went for a ride and the car wouldn't start after the motor was shut off. I have charged the battery and the Moggy happily started again but my am-meter tells me the dynamo isn't doing its job. I have got a Haynes manual but I still thought I shold ask here if there are any places I should check first on a 52-year-old car. Honestly - I don't know if the dynamo was charging last year either. The car was bought in the autumn and then just stored over the winter. Since my woman bought it she has driven it for 70 miles or so, so perhaps the battery was recently recharged by the previous owner when she bought the car... Any help would be highly appreciated.
Forgot to mention that the charging light goes on as it should when the ignition is turned on and goes out when the motor starts and is revved up a little bit and then stays off.
You ned a volt meter to check if a charge is going into the battery. With engine running and on a fast idle you should see 14 + volts at the battery. It may be the battery is kippered and not holding a charge in which case you'll have to replace it.
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Thanks for the quick reply. The battery was bought new last summer and the car started after having been turned off for six months in a freezing cold barn so I am abslutely sure the battery is okay. I checked the battery with a volt meter earlier today after the car wouldn't start. It read 11.7 volts. I charged the battery for a while and started the motor. The volt meter read 12.15 volts at all rpm's.
Make sure the fan belt is tight - but not too tight! Also - is the battery connected right way round - was it removed over winter (should have been!! ) and then possibly fitted reverse polarity!
If all ok - then probably it's sticking brushes in the dynamo - try giving it a whack or two while the engine is running and see if it starts to charge. Check for volts regulator is to join the two terminals on the dynamo together - that should throw it in to full charge mode - if that works then the problem is in the volt regulator - if it doesn't work then likely the problem is in the dynamo, although the cut-out device (beside the volts reg - under the same cover) could be faulty - although if red light goes out I would say it's ok.
The battery is connected correctly and no, it wasn't disconnected over winter. The man who owns the barn where the Moggy was stored wants to be able to move all cars stored there at all times. "Check for volts regulator is to join the two terminals on the dynamo together - that should throw it in to full charge mode " So, to do this I suppose all I have to do is to connect a jumper lead between the two teminals on the dynamo, start the motor and check the voltage on the battery. Did I understand it correctly?
Just came back indoors. I joined the two terminals and there was no change. 12.3 volts at all rpm's. I tried beating the dynamo with a plastic hammer and nothing changed. I guess this means there is a problem in the dynamo. While I was walking back in I remembered the first and only time I have repaired the charging system of a DC charged vehicle: A Ferguson tractor. As I remember it I had to connect and run the dynamo as an electric motor to so to speak teach the dynamo what to expect later on. Do I need to do something similar this time? This car was totally disassembled by he last owner so I don't know what they did when reassembling it. Otherwise I suppose next step will be to disassemble the dynamo tomorrow to see what the brushes look lke.
Yes - have a look at the brushes then - and yes - in working order it should run as a motor. You can 'teach' the dynamo the correct polarity without actually running it - just flash a wire from the non-earth pole of the battery to the small terminal of the dynamo. This was why I asked if any chance it was connected wrong way round. May be worth just trying the 'flash' trick - only takes a few seconds!
I just tried the flash trick and I don't think it made a major improvement. When the motor is idling the volt meter shows 12.17 volts and when the motor is revved up it shows 12.20 volts so something does happen, even if it is far from what is required (with the headlights turned on from 11.97 volts to 12.00 volts). It is dark in Sweden now and we noticed that the red light never goes out completely, it is always glowing at least a bit. The fact that the red light changes from shining bright to glowing - doesn't that prove that at least a little bit of action is taking place in the dynamo?
It is probably just worn dynamo brushes. Remove the dynamo and then undo the bolts holding the back plate on. Pull the back plate off and the brushes will come off with it. You can then see if they are worn.
Yes - a tiny bit - which may mean it's NOT brushes - but still worth looking into anyway! But it could be Field coil failure - in which case another dynamo will be required - or consider upgrade to alternator.
I have removed the dynamo. My first step was to put it on the ground and connect it to a battery to see if it would start turning. I noticed a little flash at the terminal but that was all. I opened it and the brushes look very okay. I cleaned the commutator and checked the ohms of the field coils. It says in my Haynes manual that the reading should be around 6 ohms. If the reading is 5 or below one of the field coils should be broken. The reading I got is 7,9 ohms so I am not really sure that is a good sign or not. I reassembled it and tested again. When connecting the small terminal nothing happened but when I connected both terminal at the same time the dynamo started spinning. I suppose this means the dynamo isn't totally dead after all but still there must be something that isn't working properly. I have been doing some telephoning today trying to find a replacement dynamo but Moggy parts aren't that easy to find quickly in Sweden. A retired car mechanic I talked to today might be able to help next week. He said there is a big risk putting a rebuilt dynamo together with an old regulator since the regulator might kill the dynamo instantly. Is that true?
If it 'motors' with both terminals joined - it's ok! It should charge nicely if you connect both terminals together on the car. Try it again! Obviously - with both terminals joined - they must also be connected to the battery non-earth terminal - the battery volts should rise to ~ 14 volts.
Okay, so I need to bolt the dynamo back on the car, connect both the wires I removed, connect these two wires to each other at the same time as I connect a separate wire from these two connected wires to the non-earth terminal of the battery. Did I get that right?
Day two: New dizzy cap, rotor etc took care of that problem. 
Today we went for a ride and the car wouldn't start after the motor was shut off. 
I have charged the battery and the Moggy happily started again but my am-meter tells me the dynamo isn't doing its job. I have got a Haynes manual but I still thought I shold ask here if there are any places I should check first on a 52-year-old car. Honestly - I don't know if the dynamo was charging last year either. The car was bought in the autumn and then just stored over the winter. Since my woman bought it she has driven it for 70 miles or so, so perhaps the battery was recently recharged by the previous owner when she bought the car... Any help would be highly appreciated.
