fusible link questions

[Steve Sassine]

On Wed, 3 Feb 1999, Clive Apps   Techno-Logicals   416 510 0020 wrote:

> > 
> > The fusable link is intended to protect the wiring harness from frying -
> > through out the vehicle. It is the weakest link in the wiring 'chain'. They
> > normally have a high temperature insulation that also protects any adjacent
> > wires from being burned.
> > 
> > It is not clear to me why you would need to put a fusible link in the wire
> > that runs from the alternator + to the battery +. You sure dont want to
> > "unload the alternator" while it is charging. And I asume that there are no
> > other wires in series with that charging wire. 
> > 
> > I'd be glad to discuss this with you further , if needed.
> 
> 
> somtimes the diode pack will short out and drain the battery or start a fire
> 
> Clive 
> 

 The fusiable link has two purposes, firstly to protect the alternator   
from over loading, and to protect sensitive electronic equipment
installed in the engine. The battery can still be over charged with out
blowing the fusilble link.
   If your car is fitted with an alternator that has a voltage regulator
mounted on the back, it is best to have a fusible link between the battery
and alternator. The voltage regulator runs in closed loop mode and usally
if the regulator is faulty the alternator will not charge at all, ie no
field current, but in the worse case the regulator may go unstable. Here
a large amount of current will be deleivered to the field winding which
will inturn give an output voltage well in excess of 20V plus. This
voltage level will take out many electronic equipment
(radio,alarm,electronic wind screen controller etc.).
 
         I have seen this happen on a toyota corona, but some of the
devices are fused seperatly to protect against high voltages.