So that might be why the charge light kept coming on!

[Smug]

The only problem with leaving the battery connected is that it can smooth the signal to an extent that its difficult to determine the humps. However, I never tried it on a bike/car. Time to dig the scope out for a play .

Trust me the beauty of using an automotive oscilloscope is that it shows details that are impossible to see with any other type of meter, even at the battery. Also saves trying to access the alternator terminals which can sometimes be tricky.

So quick and easy to do.

 

[fatnfast]

Just had a thought, I seem to remember that with bosch alternators you can do an easy test to determine if there is problem with it. If you measure the voltages at the D+ terminal and the B+ terminal on the alternator, they should not differ by more than 1volt. A simple test thats worth a try if you have no scope.

IIRC the logic behind it is they both share similar rectification diodes, and if they are functioning as they should then the voltages will be equal.

 

[warmshed]

Just had a thought, I seem to remember that with bosch alternators you can do an easy test to determine if there is problem with it. If you measure the voltages at the D+ terminal and the B+ terminal on the alternator, they should not differ by more than 1volt. A simple test thats worth a try if you have no scope.

IIRC the logic behind it is they both share similar rectification diodes, and if they are functioning as they should then the voltages will be equal.

Very astute of you, of course that is an easy quick way to check the diodes are functioning, feel ashamed I didn't think of that.
It may be necessary to run the voltage up to over battery voltage to do the check or the battery fed from behind the warning lamp would give a false reading, unless you remove the blue wire for the test.