Fusing the fan?

[Robert Myers]

If Audi decided to fuse the ground side of the fan circuit then I find 
myself forced to ask just what Fritz und Hans had been smoking that day.  I 
don't know what it was but I think I may want some of it.  :-)

At 10:29 AM 9/21/2004 -0700, Tony Lum wrote:

>Usually that's right, you fuse the power source.  In this case, Audi chose 
>to fuse the ground line (ref: Ti's post) in the 200 models.  Also the fan 
>shroud on which the motor is mounted is plastic, so there's no easy path 
>to ground.  Also the source lead is not a constant 12V but switched 
>through fan switch and relay.
>
>As for my 5000tq, rather than using the factory setup (prone to corrosion 
>and opening without warning), I used a 80A Buss fuse with straight 
>legs.  This fuse is commonly available at most FLAPS and has a black 
>plastic case.  The fan's ground return stud is long enough to thread a nut 
>on to keep the stud's through penetration short.  So you nut the fuse onto 
>the ground lead and use a very short bolt onto the other leg of the fuse. 
>The extra nut on the ground stud keeps from shorting out the fuse.  Aim 
>the fuse's inspection window up so that you can see the fuse link 
>clearly.  I got this tip from another lister years ago and it takes all of 
>10 minutes to install.
>
>Regards,
>
>Tony
>urq #DA900302
>
>-----Original Message-----
>From: quattro-bounces at audifans.com
>[<mailto:quattro-bounces at audifans.com>mailto:quattro-bounces at audifans.com]On 
>Behalf Of Robert Myers
>Sent: Tuesday, September 21, 2004 7:58 AM
>To: Pat Korach; Hoffman Anthony J A1C 552 CMS/MXMVC; 'Ben Swann'
>Cc: quattro at audifans.com
>Subject: Re: Fusing the fan?
>
>
>NONONONO!!!  A fuse should always act to shut off power to the protected
>part of the circuit.  Put it on the "hot side" of the circuit. If a fuse on
>the ground side of the fan blows there will still be a nominal +12 volts
>supplied to the fan.  If the fan is short circuited to ground - first there
>is no protection and second, it's unlikely the fuse will even blow because
>the current drain will flow directly to ground bypassing the fuse.  It
>would not matter a whole lot whether the fuse blew or not under those
>circumstances.  How good are you at fighting electrical fires?

Bob
Random Bushism: "I don't want nations feeling like that they can bully 
ourselves and our allies. I want to have a ballistic defense system so that 
we can make the world more peaceful, and at the same time I want to reduce 
our own nuclear capacities to the level commiserate with keeping the 
peace."  George W. Bush, Des Moines, Iowa, Oct. 23, 2000
_____
Robert L. Myers  304-574-2372
Fayetteville, WV, USA
'95 urS6 - Cashmere Grey
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