Originally Posted by Jeremy5848

A faulty voltage regulator (which is part of the alternator but separably and easily and inexpensively replaceable) could do all of those things. If you have a voltmeter, you could try monitoring the voltage while you drive for the next few days. You can get a lighter plug and connect the voltmeter to it, then plug it in the lighter socket. During pre-glow the voltage will be as low as 10 Volts. Once the engine starts and the glow plugs go off, the voltage will rise but should not exceed 14 Volts, more or less.

Jeremy