Ignition light

[myoldjalopy]

OK - to test the dynamo you need to remove the F and D wires from it and bridge the two terminals together. Then connect your voltmeter red wire to either of the two bridged terminals and the black wire to earth (as you have a -ive earth dynamo system). Start the engine and carefully increase its speed. The voltage should increase but don't let it rise much above 16v as, now being disconnected from the regulator and thus unregulated, the voltage can rise too high and damage the dynamo. If a low or no reading is obtained the dynamo is faulty.
The other, less accurate, way is as I described earlier - i.e. with dynamo connected up correctly, remove fan belt, remove cover of control box and press down the cut-out contact (the one on the right hand side as you face the car...do not press the regulator contact). The dynamo should then run briskly as a motor. Make sure the cut-out disconnects again after this test.
Yes, there is current to the voltage regulator when the ignition is off - which is why, if the cut-out contacts stick together and don't release when the engine is switched off and the dynamo stops generating, the ignition light will stay on even when the ignition switch is off - not good as then the battery will be sending current to the dynamo which, if the fan belt is connected, cannot run as a motor and will be damaged.

[soilman]

Hi did the test, got erratic readings, hard to hold those terminals whilst revving the engine, but it did show almost 20 volts, also did the other test and the Dynamo ran well. What now? Tempted to buy a control box (did clean the points)as can’t see problems with wiring?

[myoldjalopy]

Yes, you do need three hands sometimes when working on these cars!
But, if you are getting readings of up to 20v from the dynamo, and it will run as a motor both in and out of the car, and the wiring and connections are good then, from a distance, I guess the control box has gone kaput. I would replace it - they aren't that expensive - but be aware that modern ones aren't as good a quality as the originals, nor do they last as long (in my experience). You can get reconditioned 'old' ones but they are quite expensive, I believe.
Your other option, especially as you are running your car -ive earth anyway, would be to get an alternator conversion kit.

[geoberni]

You could always just see what's out of adjustment on the Regulator.
The manual does give instructions, either Section N9 or N51, depending on the regulator model.
Just 'cleaning' the contacts doesn't help if it's not set up right.
Regulators are simple, pretty temperamental and fiddly sometimes, but still a simple concept.

Try putting "lucas voltage regulator adjustment" into youtube search and there's loads of info there.

[soilman]

Just had a shocking experience, thought would check the wiring behind the dash, something was loose the next thing I know smoke coming out of dash, had to pull the connection off of the battery to stop it.once the smoke cleared it wasn’t as bad as I thought. One of the black cables connected to E on the control box had been destroyed.I found the other end behind the centre speedo disconnected?not sure what it came off of, but looking at the schematic it goes to the screen wiper switch?
So once I had made safe I connected up the battery and everything worked ok, so can I just replace the cable from E to the screen wiper switch?, and why did this happen? The cable should go to earth, so if it touched I powered cable by mistake would that cause this catastrophic result?

[soilman]

Just had a shocking experience, thought would check the wiring behind the dash, something was loose the next thing I know smoke coming out of dash, had to pull the connection off of the battery to stop it.once the smoke cleared it wasn’t as bad as I thought. One of the black cables connected to E on the control box had been destroyed.I found the other end behind the centre speedo disconnected?not sure what it came off of, but looking at the schematic it goes to the screen wiper switch?
So once I had made safe I connected up the battery and everything worked ok, so can I just replace the cable from E to the screen wiper switch?, and why did this happen? The cable should go to earth, so if it touched I powered cable by mistake would that cause this catastrophic result?

[soilman]

Sorry should have been posting this in the electrical section. I have a retired old school auto electrician coming to sort out, said he cut his teeth on morris minors. Thanks for all the advice will post he’s findings.
Regards Bruce

[myoldjalopy]

You must have created a short circuit somehow. 'E' on the control box is an earthing point, the other end must have touched a live wire, or connection. If you have now removed the wire then - if the other end was connected to the wiper switch - the wiper should now not work...does it, or no? You say 'everything worked OK' but , if your suspicion is right, the wiper should not work now. I think the interior light is also connected to 'E' on the control box, so it may be that. Not sure if you have one in your car. Nor what wiring 'modifications' anyone may have made in the past
I think you need to get the speedo and glove box liners out and have a good look round (with battery disconnected this time!). It should be obvious if it came from the wiper switch. Check there are no bare wires in behind there. Once you are sure where it should be connected and, assuming you can't find any bare wires, or anything else suspect behind the dash, connect it back and reconnect the battery - but be ready to disconnect again quickly if anything starts to burn again.

[myoldjalopy]

Sorry Bruce, must have missed your last post somehow....yes, the auto-electrician should be able to sort out your issues - do let us know the outcome.

[soilman]

Hi, yes I have taken out the gloves boxes and speedo, found the other end of the burn earth wire from the control box loose?doesnt seem to have come off the wiper switch and the wipers still work?in fact everything still works, haven’t got a interior light.
Any how spoke to this old gentleman who reassured me that it be ok and he would sort on Wednesday, so I will come back and up date the threadmanythanks for everyone’s support

[soilman]

Ok Dudly came and check the car, the problem was the control box, which what I had suspected after checking the Dynamo and wiring.i had already ordered the control box and it is fitted and the problem solved.
As for the loose wire behind the dash which earthed and burnt out, he said it was bad luck and removed it as it was surplus to requirement

[myoldjalopy]

Good work! And let us hope the control box gives long service. The originals lasted decades but I don't think the new ones are of the same quality.
The burnt wire is a bit of a mystery though - maybe someone previously fitted a component that was later removed but left the earth wire behind? With the age of these cars there has been plently of time for previous owners to have 'tinkered' with any part of it - at any time.....