Fusing the fan?

Ben Swann benswann at comcast.net
Tue Sep 21 20:30:48 EDT 2004

Great info Ti!  I should have read through the 100 or so posts I have in my
inbox before asking the question that this seems to answer.  Just
reiterating your post for continutity as well as passing it on.

80 AMP Fuse!  WOW!  That is a lot.  Isn't all this current passing through
the fusebox?  Or is there just the low speed circuit that goes through the
wiring at relay position 2?

I simply inserted some spade lugs and inserted the fuse into them and
insulated the lugs and mounted on the fan frame.  I would guess there are
many variations on this.  So maybe the 60 AMP fuse I have in there now is
not overkill and I should have expected the 30Amp fuse to blow - it didn't
right away, but did eventually.

----- Original Message ----- 
Hoffman Anthony J A1C 552 CMS/MXMVC writes:
> How have some of you fused the fan? I have two 5000's recently acquired,
> would like to do this. What amp rating is required?

Below are a quotes from several related posts in 1999 on this list.

 R 1 3 5  Ti Kan
 |_|_|_|  http://www.amb.org/ti
   | | |  Vorsprung durch Technik
   2 4 6

Cooling Fan Fuse Modification

In addition to their many excellent qualities, the 5kt/q (type 44) cars are
well known for their
tendency to incinerate the left main engine compartment wiring harness when
the cooling fan
seizes. There is usually a warning squeak from the fan bearings giving the
owner between 2 hours
and 2 months advance notice of impending doom. See the past "Audi Bonfires"
thread, for example.

There have been several solutions presented on the list, but I feel the most
thoroughly engineered fix
has been one designed by Audi. A neatly housed and mounted 80A fusible link
was incorporated
into the USA 200s at some point(?). I first noticed this fix in a 1991 200q.
Fortunately, this modifi-
cation is as easy as pie for any type 44.

The parts list: (Audi P/Ns are given for the hardware, but you can always
eyeball this and
use whatever you sweep up off the garage floor.  I ordered this stuff from
Carlsen when I bought
the box, bracket and fuse; for the extra $2, you can get it exactly right.
BTW, your Carlsen
prices should be lower than Retail.)

Qty.    Item            Audi P/N        Retail $

1       fuse box        281 937 505 A   10.89
1       bracket         443 971 845 AM   9.55
1       fuse link, 80A  N 017 125 3      1.30
2       screw, M5x8     N 014 128 11     0.45
2       lock washer     N 012 005 3      0.15
2       screw, tapping  N 013 966 26     0.38
2       washer, flat    N 011 556 2      0.15

Other materials:
1 foot  10 AWG wire for automotive service, preferably
        brown to match the European color convention.
2       crimp terminals, 10-12 AWG (yel.), #10 ring
1       crimp terminal, 10-12 AWG (yel.), 1/4" ring
3-4"    shrink tubing, 1/4" to 3/8" diam. (optional
        for insulated crimp terminals)
1 or 2  cable ties (optional)

Tools: 10mm wrench, medium Phillips screw driver,
       high quality crimping tool appropriate to selected
       terminals (perhaps borrowed), heat gun, wire


a. It is proper to disconnect the battery before undertakingany wiring
modifications. However, if the engine is
STONE COLD and if you email me a signed liability waverin advance, it is
possible to proceed with reckless
disregard for safety and leave the battery connected since the effected
wiring is strictly ground side.
Keep the wrench away from the positive fan motor terminal and your face
clear of the fan blades just in case I'm a
lying dog.

b. It is assumed that you know how to properly fit crimped wire terminals
and have the proper tool.
Soldered joints can be used but are emphatically not recommended for
automotive wiring connections
for the best long term reliability. However, if you don't have access to a
_good_ crimping tool, soldering may be the better choice. A cheap, single
acting "electrician's"crimper will definitely not provide sufficient
to correctly crimp such heavy terminals. (I'm not interestedin a crimp vs.
solder or crimp vs. solder & crimp thread.
Just suit yourself and take your best shot.)

c. The fuse link box has two link positions. This fan motor circuit only
uses one of them. Please don't swoon
and hurt yourself while contemplating the infinite possibilities.

d.  I haven't looked at every type 44 model. Details could certainly vary.
Determine if the following
instructions make sense for your vehicle before starting so you will have
been able to work out any necessary
corrections ahead of time. Easiest to do with partsin hand.

1. Establish that the shrink tubing, if used, is sized  to fit the selected
crimp terminals. Mandatory for
   uninsulated terminals.
2. Mount fuse box to fuse bracket with tapping screws  and flat washers. (I
suggest mounting so that
   the hinge of the cover is up^ in order to better   resist water entry. It
would be a good idea to
   test fit the bracket in the car first just so   that it is completely
obvious which end   will be "up" and that the bracket's mounting   tab or
ear bends away from the surface the box   is attached to.)
3. Remove the right-rear mounting screw from coolant   reservoir. This screw
also retains a mounting
   clip for the left-front ABS sensor connector   and a small aluminum
wiring harness support "Z"   bracket.
4. Remove this aluminum "Z" bracket (for ABS unit   wiring harness) after
releasing the plastic wire
   clip from "Z" bracket hole. Leave plastic clip on   harness. Throw "Z"
bracket into the "save for use
   in next lifetime" bin.
5. Mount bracket/fuse box. The stacking order is new   fuse box bracket,
then ABS connector clip, then
   coolant reservoir tab. This all goes together   nicely like bread and
butter. The fuse box
   now faces the engine.
6. Leave the dangling ABS wiring clip unattached   until the wiring is
complete. Be comforted
   by the fact that the new fuse box bracket has   a hole just the right
size and in just the right
   place to accept the clip nibs. (Ya just gotta   love German engineers at
times like this.)
7. Remove the cooling fan motor's ground lead (single   heavy brown wire).
8. Cut off (oh go ahead) the terminal on this lead   since it ought to be
replaced by a smaller size
   ring to match the fuse box screw size. You shade   tree electricians
might spit at this but I really
   think it necessary for a good installation. Cut   the wire as close to
the terminal as possible to
   allow good reach with the remainder.
9. Install a #10 ring terminal (metric size 5 mm?)   on this fan motor
ground lead. Slip a piece of
   shrink tubing on beforehand to avoid that stupid   feeling. Carefully
apply shrinking heat.
10.Bend the ground wire back toward the new fuse box and   loosely connect
this terminal to one of the forward-most   box screw terminals. Use a 5Mx8
screw and a lock   washer. The finished stack will be link, ring terminal,
   lock washer. (The fusible link, itself, can be   easily dropped into
position under the ring terminals
   after all the wires are in place.)
11.Make up a 10 AWG connecting wire with a #10 ring   terminal at one end
and a 1/4" ring at the other.
   You should test fit this in the car. In my case,   11 1/2" from ring
center to ring center allowed a
   nice neat loop from a rear fuse box screw terminal   to the fan motor
along side the ABS unit harness,
   including routing through the aforementioned plastic   wiring clip.
Again, plan ahead as needed for shrink
12.Route the new wire from the rear fuse box terminal,   which opposes,
front-to-rear, the one you've used for
   the original fan motor ground wire, forward along the   ABS unit harness,
through the wire clip and down to
   the fan motor's ground terminal.
13.Drop the 80A fusible link into place under the ring   terminals, snug
down the screws, coat the connections
   with battery terminal sealant or similar and snap the box   cover shut.
(The box is not weather tight but is well
   located considering it's under the hood. A little anti-corrosion
protection would be a good idea.)
14.Finalize the wiring dress and snap the wire clip   into the bracket hole.
Use a cable tie or 2 if you
   like. I found this not particularly necessary due to   the existing clip,
the short run and the stiffness of
   the 10 AWG wire.
15.Step back and admire your official factory upgrade.
16.Sleep at night.

Have fun and best luck,

DeWitt Harrison
The # of the thermal fuse we use isCB-50 (it is a Borg Warner #)
Should be available from any good parts house.....

Below is another way to install a fusible link to protect your cooling

Here is the information regarding the fuse, I picked mine up at Kragen
It is made by "Buss Fuses" (Japanese made fuse)
It is BP/FLB 70 (70 Amp) or you can get BP/FLB80 (80 Amp)

Install procedure:
Disconnect ground wire (brown) at fan motor (10mm nut)
Connect fuse to fan motor post using above nut
Connect ground wire to the fuse using a 10mm short bolt and a nut
Make sure you buy two fuses (for replacement purpose)

You are done, isn't that peachy?


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