Type 44 Radiator Fan current draw

Bernie Benz b.benz at charter.net
Tue Sep 21 22:50:25 EDT 2004

The Audi "after thought" fuse is sized to protect against the locked rotor
current thru a rotor resistance of <0.175 ohms, the resulting 80+ amps is
capable of frying all but the battery cable.  The fan's normal start up
current is considerably less than the locked rotor current because of the
armature inductance and subsequently the back emf of the accelerating rotor.
Further, its a most unlikely condition in the 44 chassis Audi system that
would demand 3d stage, full alternator voltage, for a fan start up.  Thus,
your 30A fuse would sufice for all but the most unusual of startup

Audi could have just as well, if not better, placed the fuse on the +, hot
side of the motor but didn't, no big deal IMO.


> From: "Ben Swann" <benswann at comcast.net>
> Organization: Swann
> Reply-To: Ben Swann <benswann at comcast.net>
> Date: Tue, 21 Sep 2004 20:05:08 -0400
> To: <quattro at audifans.com>, <200q20v at audifans.com>
> Cc: Ben Swann <benswann at comcast.net>
> Subject: Type 44 Radiator Fan current draw
> What is the nominal and peak load one can expect to see on the type 44
> radiator fans.  The one I though was locking up because it blew a fuse seemed
> to be working as well as the others I compared it to.  It like the others
> seems to take a sizeable initial current draw - no actual numbers here.
> During operation current is enought to get a no. 12 wire fairly hot when the
> wire is used to jumper the fan in relay position 12.
> The mechanic who said he did a load test on it indicated it drew 45 AMP.  The
> 30 Amp protective fuse I had installed in the return to ground line blew after
> 2-3 months of operation.  I installed another 30A fuse and drover the car for
> some time with it not blowing.  I then replaced it with a 60 amp fuse.  What
> is the actual fuse that Audi put in the later type 44s with the fuse option?
> Any other helpful information on the fan operation and current draw would be
> appreciated.  I am trying to determing if replacing this fan would be prudent.
> A new fan is like $400 and though I have used fans, they seem to operate the
> same way this one does based upon my intial simple tests/observations.
> Vehicle/Engine in question is '87 rebuilt 2.2l turbo installed in a '88 5000
> quattro avant, but I assume the information spans the majority of these cars.
> Ben
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