Sounds like a good reason to install a properly sized fuse inline with a
wire gauge upgrade.  Perhaps an alternator upgrade would also be in
order?  Any voltage drop across your headlight/radiator fan/blower motor
supply wire implies waste heat being dumped from the wire.  Power =
current x voltage.  A 2 volt drop in a supply wire with a 20 amp load is
40 Watts wasted.

On 11/17/2013 6:35 PM, Dennis Haynes wrote:
> Most auto equipment will work over a large voltage range but performance
> does suffer. However it is not by accident or even cost savings that the
> wiring is "undersized". As the system gets loaded down thee resistances help
> to control the load on the alternator. Also, as so much wiring is not over
> current protected the smaller sizes also help to limit or control fault
> currents. Yes those wires can act as fuses hopefully burning up enough to
> open before the van is gone.