Ignoramus13864 wrote:



It definitely needs to charge at idle.

You MAY be able to modify the alternator to get it to charge at idle. The
regulator may be dropping out at low voltage. Possibly putting a resistor
across the regulator circuit might cause it to deliver a little current even
at a low voltage.

But, the real problem may be that the new alternator is not designed for
running off this Diesel engine. Depending on the engine's idle speed and
the crank pulley diameter, it may not get the alternator spinning fast
enough. Possibly the original alternator (do you still have it?) had a
different rotor or stator winding pattern to accomodate this. If you still
have the old alternator, you might be able to replace the rotor brushes or
rectifier diodes to get it to work again.

1250 RPM sounds pretty low. Most small cars have engines that idle around
800 - 1000 RPM, and with a 3:1 pulley belt ratio, the alternator would be
spinning at least 2400 RPM at idle.

Jon