Tonya,

Occam's razor says the most obvious answer is probably the correct one. 
 Which means that the charging system is probably malfunctioning.

I suggest that you connect a voltmeter up to the battery ... the cigarette 
lighter socket will do fine ... and when you catch the vanagon with the 
idiot lights on:

1) Turn on lots of stuff, like the headlights and heater blowers.

2) Hold the engine at about 2000 rpm.

3) Note the battery voltage.  It should be about 13.5 volts
   minimum, nearly 15 volts if it's very cold out.

Mike