Fusing the fan?
ti at amb.org
Tue Sep 21 11:13:38 EDT 2004
Hoffman Anthony J A1C 552 CMS/MXMVC writes:
> How have some of you fused the fan? I have two 5000's recently acquired, and
> 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
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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
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 undertaking
any wiring modifications. However, if the engine is
STONE COLD and if you email me a signed liability waver
in 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
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 pressure
to correctly crimp such heavy terminals. (I'm not interested
in 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
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 parts
1. Establish that the shrink tubing, if used, is sized
to fit the selected crimp terminals. Mandatory for
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"
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,
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 fan
Here is the information regarding the fuse, I picked mine up at Kragen auto
It is made by "Buss Fuses" (Japanese made fuse)
It is BP/FLB 70 (70 Amp) or you can get BP/FLB80 (80 Amp)
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?
More information about the quattro