FW: RE><E28> Aux Fan fuse problem

["Chao, Harvey" <harvey.chao@xxxxxxxx>]

> ----------
> From: 	Chao, Harvey
> Sent: 	Thursday, December 3, 1998 10:49 AM
> To: 	'Andrej Gaspari '
> Cc: 	'Bri-e'
> Subject: 	RE><E28> Aux Fan fuse problem
> 
> Knocking on wood, I haven't personally experienced this problem myself,
> however:
> 
> In general heat (to soften the fuse box) comes from excessive current draw
> through a resistance. 
> 
>  IF the current is too high, it could be the fan motor is drawing
> excessive current.  Most likely if this is so, the fan bearings are going
> bad generating more drag on the fan shaft causing the current draw to go
> up. As the equation in the next para. indicates, and increase in current
> can have big consequences in heat generation at any point of resistance
> (motor windings, fuse contacts, and low speed voltage dropping resistor
> are the three major places .
> 
> If the resistance has gone up, it is most likely at the point where the
> heat is being generated, i.e. the contacts for the fuse.  This kind of
> fuse and fuse holder has a known reputation for oxidation of the
> contacts/fuse which increases the resistance at the contacts.  The heat
> generated is power expressed in the equation P(watts) = (amps x amps) x
> resistance.  I try to remember to pop the cover on my fuse box and twist
> each fuse a full turn about it's long axis every 6 months on the theory
> that this movement will rub the mating surfaces clean to fresh/clean
> unoxidized metal.  
> 
> Note additionally that if it is increased current draw, the wattage/heat
> dissipated by the low fan speed dropping resistor will also go up and may
> soon exceed it's rated/actual capacity to dissipate this much heat and
> shortly fail.  I believe that this is a $20-30 part ( for a simple power
> resistor!).
> 
> Harvey
> 

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