Dynamo non charging

[chickenjohn]

As a follow on to this- I checked the fan belt- and it was loose. Dynamo tightened up now and the car actually seems to start a little easier as well. Lets hope thats all it was.

[Onne]

I have found the culprit. The voltage regulator was faulty. So were nr 2 and 3, but nr 4 works a treat, delivering a healtly 13.5V to my battery.

Thanks for the help

[southerly95]

I picked this thread up looking for solutions, it doesn't say whether you connect +ve or -ve leads on the multimeter to the dynamo terminal? Could someone advise please, many thanks.

ONNE, I quote from the workshop manual. switch off all accessories and
disconnect the dynamo leads Dand F. connect the dynamo terminals with
a short piece of wire then start the engine and run at NORMAL running speed. Connect a voltmeter on 0-20v scale between the dynamo terminal
and the dynamo body. GRADUALLY increase engine speed when the voltage reading should rise rapidly but do not rev engine( approx 1000rpm should suffice) do not let reading reach 20 volts.
The clues from this are: NO READING=check brush gear. LOW READING
(approx 1V)=possibly field windings faulty. LOW READING(approx 5V)=
possibly armature winding fault. If you manage this the next stage will
identify faults further along the line.

[alex_holden]

If the car is positive earth, connect negative to the output terminal and positive to the dynamo body (or any good earthing point really). If the car is negative earth, reverse them.

If you have a digital multimeter it'll just show a negative figure if you get it wrong, but an analogue meter will push the needle backwards against the stop and possibly damage it.

[southerly95]

It's negative earth and I followed your instructions, I have an analogue multimeter. Set to 10v dc it goes off the scale and at 50v it shows as about 14-16.

I refurbed the dynamo four weeks ago with new points (can't remember the proper name of them ) - symptom was the red light glowed faintly and wouldn't go out during normal running. The refurb seemed to stop but then returned a week ago. This morning I cleaned the regulator contacts and the ignition light is bright red and doesn't dim at all now, hence testing the dynamo. Thoughts welcome

[alex_holden]

With an analogue meter, always start with the range set higher than the voltage you want to read, and only reduce it if you're sure it fits within the next range down.

The carbon things in the dynamo are called brushes.

What did you use to clean the regulator contacts? It sounds like there's a bad connection somewhere, but because messing with the contacts has made the problem worse I'd look there first.

[southerly95]

Aha - I redid the contacts gently using fine grade wet and dry and cleaned them thoroughly with a fine cotton cloth and is now working ok, many thanks