Re: [DML] Fuse 7 - Engine Control - MELTED

[Paul Gress <pgress@xxxxxxxxxxxxx>]

John Hervey wrote:
>   
>> I've seen this before on other Deloreans.  And the PO of my car had it 
>> melt on the fuse box.  To repair it he spliced some new line and an 
>> inline fuse.  This has been working great since I've owned the car (7 
>> years).  Today my car died while driving.  Fuse 7 not only blew, but 
>> totally melted.  Does anyone know why this happens?  I keep my fuses 
>> clean, but I have to be honest, I haven't cleaned this one in a few 
>> years.
>> Any ideas would be appreciated.
>>
>> Erik
>> 04512
>>     
I'm going to try to really simplify my explanation.

A resistive load is the simple load everybody thinks of, such as a light 
bulb.

An inductive load utilizes magnets to create a load.  The way is works, 
is if your using an electro-magnet (such as the ones when you were a kid 
with wires around a nail), while the magnet is developing it's magnetism 
(immediately after attaching the wires to a voltages source such as a 
battery), the load is inductive.  The circuit is using the current to 
charge the magnet.  After the magnet fully charges, the magnet stops 
drawing current, then the load turns resistive (the wires).  If the 
length of the wires (around the nail) measure approximately 1 (one) ohm, 
and the inductive load is 50 ohms (while magnetizing) the circuit will 
be inductive while the magnet is energizing, and resistive after fully 
energized.  The magnet is called saturated when it fully magnetizes, 
this is the point where it now becomes a resistive load.

Now for a practical point of view, a speaker.  A speaker is a bunch of 
wires around a magnetic core.  It may be rated at 8 ohms, but if you 
measure it with a ohm meter it may only measure 1 ohm.  As long as the 
speaker is moving and changing it's magnetic charge, the magnet is the 
load (inductive).  If you turn up the volume beyond the speakers rated 
power, you will magnetize the speaker faster, maybe to fast that the 
magnet saturates (magnetizes fully) then the load turns resistive 
(because it's one ohm and draws much more current) and you have a good 
chance of burning out the speaker.

Paul





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