alternator pulses until warm , if batteries are charged perfect it doesn"t pulse
I suspect you are watching the volt gauge and not performing an alternator analysis.
There are no glow plugs, when the temperature is below 55 degrees the engine intake air heating grid is switched on and off for cold operation until the coolant temperate reaches a certain temperature. The heating grid draws 90 amps, this can exceed the output of the alternator during idle. You may see the volt gauge move from 14 volts to 12.5 volts while engaged, this is normal.
The effect is greater if there is one failed battery. Disconnect one battery and test the batteries independently.