Morris Minor Owners Club

Could anyone help us we are busy scratching our heads on this. We bought a car last week and managed to limp it home with what the aa dignosed as a failed dynamo, we fitted another that didnt work now another and that doesnt work either. We wanted to go to the MMMOC meeting tonight I have heard you need to remagnatise these sometimes I have a positive earth vehicle. Ive tried opposite to the "converting to neg earth" advice e ie Big spade connector on dynamo with a wire to the positive battery for 10 seconds hoping to "convert to positive"and still nothing it seems very odd that 3 dynamos arent charging. We are wondering if the second and third dynamos we have got are from neg earth vehicles . PS thanks to the guy from Wigan for the free dynamo I think its my skills which are lacking here !

It's the SMALL terminal you need to touch with the wire!! Or -as I mentioned earlier - both together (with fan belt slack/removed) if you want to test if the dynamo works. It will run as a motor if it is working when you do this.

Small spade to positive earth ? I just tried small spade to positive with no joy grrr so frustrating anything else I could try other than your motor fix ?

No, as BMC says, small and large blade connected together to the non-earthed battery terminal (so in a positive earth situation, connect momentarily to the negative battery terminal)

You can leave the fan belt on, you will see the dynamo "twitch" as it tries to act like a motor.

Don't leave it on for more than a moment though.....

But you must touch it to the NON EARTH terminal of the battery!

Thanks for your help guys didnt hear it twitch and red light still on so it might be a case of fourth time lucky !

It is EXTREMELY unlikely that all the dynamos are faulty.... Test them properly - and find one that 'motors' . Remember - you must join both terminals together to a length of cable - and contact that to the NON EARTH connected side of the battery. If it still doesn't provide a charge - then the fault will be in the regulator control box.

Try checking the wiring to the regulator box on the bulkhead, and if that is correct, then swap the regulator. Are you relying only on the ignition warning light, or have you checked for charge in other ways such as a voltmeter, or seeing if the headlights get brighter when you rev the engine? Are the dynamos new or secondhand?

Is the red light definitely connected to the dynamo - if you remove the dynamo connections, and switch on the Ign - is the red light then OFF ? I ask because it's not unknown for the warning lights to be mixed up in the back of the speedo!

Ive taken a look at the regulator and its been replaced and Im wondering if thats playing up again . Ive turned the charge screw to see if that was misadjusted with no joy. My friends dropping his multimeter off later so Ill try that. Ive taken the 2 wires off the dynamo and the lights still on , is that wrong surely its there to indicate lack of current so off would be the same as not working ? Ive tried revving the engine and the lights stay the same brightness. These are second hand dynamos the first off ebay and the second kindly donated to me from a chap off the forum both untested but I just cant believe 3 are at fault

If the red light is still ON with dynamo disconnected - then it's probably NOT the IGN light - unless there is a very strange fault with the regulator. Don't mess randomly with the Regulator adjustments! Have you actually checked if the battery is being charged? Good fast idle with everything connected - - what's the battery volts? And - take the wire off the oil pressure switch.......is the red light still on now?

Yes the red light is still on if the oil pressure connector removed. Ive never used a multimeter before could someone please explain how use the meter what setting I put it to to and which prong goes where and what readings I should get when I

1. test if the battery is being charged
2. test the dynamo from the 2 spade connectors at the back of it when the engines running
3. test the regulator

sorry electrics arent my strong point. A friend of mine tested the last dynamo directly from the spade connectors with the engine running and it gave 0.5 volts and the first one was tested by the AA and gave the same

To set the meter connect the red and black leads to the + and - symbols on the front of the meter, set the voltage range to 0-20v dc. Connect/Touch the probes of the meter on the Plus and Minus signs on the battery. The battery with a good charge will read 12.5v.
Start the engine and connect the leads again, rev the engine and see if the voltage reading of the meter goes up to around 13.5v. If it does then the dynamo is working, if not then I suggest you get an auto electrician to take a look or maybe a club member?
Dynamo`s do not have a regulator it is the regulator on the bulkhead that looks after the rate of charge. The charging cucuit of a minor is fairly basic and generally the only thing that fails is the brushes, but as you are on your 3rd dyamo it seems that there is somthing more amiss.

I suggest you google for a Morris Minor workshop manual and download it as there is a section in there that details how to check the dynamo for output.
I also notice that you have recently bought the car, did the previous owner know anything about the fault or has it just started?

Thanks Richard we are going to try it later when my friend comes over. Are you the Richard we bought the bumper off on Sunday ? I think it may be worth trying another regulator Ill try and get hold of another, I assume the battery couldnt be at fault or a loose belt ? The dynamo is spinning so I imagine its a no to my last question
Mark

Don't rush in to another regulator! DO THE TESTS on the dynamo to see if it motors! And you need to find out what is causing the red light- is there a wire to the top of the oil filter casing? If so - pull it off and see what happens.

I tried a screwdriver against both spade terminals and a wire from the neg battery terminal to the screwdriver I go a few sparks and a small puff of smoke but it didnt twitch as you said I guess I could try the meter red prong against the large terminal and black against the small and start the car and see if the meter reads high and the other comment from richard re the battery then the regulator change then I think it will be a auto repair guy job

If you measure the output of the dynamo at the terminals at the rear of the dynamo don't rev the engine too high or let the output go above 15volts otherwise you may damage the dynamo. The reason being that dissconnected from the regulator you cannot regulate the voltage output of the dynamo and it is too easy to damage it.
Test the dynamo at the battery end first as I said earlier with a multimeter on the battery and see what voltage reading you get.
Before changing any parts we need to see the results of the basic tests first.
If you are stuck for a basic wiring diagram use the one at the top of this section to give you an idea of how it all works together.

You seem determined to avoid following the advice offered - or to correctly carry out the various tests suggested.... So yes - good luck with an auto-electrician.. We can lead the horse to the trough, but we can't make it drink.......

Try a brand new dynamo, these are available for £70 or so. It's possible that all the second hand dynamos you have are faulty. I've been there myself, tried a few customer supplied 2nd hand dynamos. On opening them they all had either signs of damage to the armature or worn brushes. Fitting a new dynamo solved the problem or the the dynamo is otherwise ok new brushes.

Oh and as said are you sure the speedo lights are correctly wired up? If the light is still red with the dynamo disconnected.

Hey no need to be so harsh Im trying my best ! I tested the battery with multimeter and revved the engine with no increase in volts and tried to get a reading of the back of the dynamo whilst the engine was running and electrocuted myself twice ! Ive noticed the battery leaking a little after charge I think some acid has gone onto the car body Ill have a clean up first before going back in armed with rubber gloves save me turning into frankenstein