Fusing the fan?

Tony Lum tlum at flash.net
Tue Sep 21 13:29:48 EDT 2004

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.


urq #DA900302 

-----Original Message-----
From: 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?

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