[V6-12v] Radiator Fans not switching in correctly...

[Wilfried Link]

I had similar problems with my 95 A6. Turned out all
switches and relays were fine. The cause was one of
the electric cooling fans was worn out -- the carbon
brushes on the motor just plain too short to
consistently make it run. After replacing it,
everything worked fine again. About a year later, the
other fan motor stopped working as well. Replace it,
all is well again. The car had about 190,000 miles on
it. If you can find a shop that will replace the
brushes, consider that option -- the brush contact
area was too worn on mine, but the new fans vibrate
noticeably when compared to the silky smooth original
ones.

Wil
95 A6 Avant

--- Poncho <ponchojuan66 at yahoo.com> wrote:

> SOunds like its running correctly.  The sensor on
> the
> raditor is actually a switch to control the fan (
> through the resistor block).  This is configured
> differently on depending on number of issues.
> 
> Normally the fan will come on when the temp guage
> reaches just ubove top dea center on the guage.  It
> will typicallu stay on for a fe mimutes and shut
> off. 
> You will not notice much movement in the guage.  The
> reason is the water is cooled in the radiator and
> the
> guage "sensor" is the one on the heater hose behind
> the engine.
> 
> The whole thing is working IF the you keep the car
> idling and it stays around the middel of the guage.
> 
> Under way ( 30MPH or more) , it should eventually
> return to the 1/3 mark.  IF you don't trust it, you
> can check the temp witha a meter a temp probe.  But
> I
> would not worry too much.  Aslo make sure you are
> running the right mix of antifreeze and the
> expansion
> cap is ok.
> 
> poncho
> 
> --- Tom Christiansen <tomchr at gmail.com> wrote:
> 
> > Marc, James:
> > 
> > The external thermometer is a completely different
> > circuit. The sensor
> > is located behind the lower grille by the port
> side
> > foglight. It's a
> > NTC resistor. It's resistance at ~70F/20C is
> roughly
> > 1500 ohm (easily
> > verified with an ohmmeter). It has a 2-pin
> connector
> > that's wire-tied
> > to the bottom of the battery 'shelf'. From there,
> > the wires go via the
> > fat wiring harness into the instrument cluster,
> > where it ends up as
> > pin 2 in the connector for the thermometer
> display.
> > It's the brown
> > wire with a yellow stripe. Measure the resistance
> > from that
> > yellow/brown wire to ground and you should get
> 1500
> > ohm at 20C/70F.
> > 
> > The reason I know is that that wire got pinched to
> > ground when I
> > replaced the heater core. I recently ran another
> > wire to get the
> > display to work. It was showing 'E' all the time.
> > Drove me nuts...
> > 
> > Aside from the 'E' in the display I noticed no
> > ill-effects of having
> > that wiring messed up.
> > 
> > Tom
> > 
> > On 8/29/06, James Whitehouse
> > <james_whitehouse1 at yahoo.co.uk> wrote:
> > > Marc,
> > >
> > > It's a valid question, but I don't know what
> > sensor reads the outside temp -
> > > which one are you thinking of, and how would I
> > check whether it's accurate?
> > >
> > > Thanks for the zinc paste info!
> > >
> > > Cheers,
> > > James
> > >
> > > > -----Original Message-----
> > > > From: The CyberPoet
> > [mailto:thecyberpoet at cyberpoet.net]
> > > > Sent: 29 August 2006 20:42
> > > > To: James Whitehouse
> > > > Subject: Re: [V6-12v] Radiator Fans not
> > switching in correctly...
> > > >
> > > > here's some more info on those zinc-suspension
> > pastes:
> > > > http://sw-em.com/anti_corrosive_paste.htm
> > > >
> > > > Q: are you getting a valid reading from the
> > outside temp sensor? If
> > > > it's reading way too low or not at all, it
> might
> > affect the system
> > > > logic for the fans...
> > > >
> > > > Cheers
> > > > =-= Marc
> > > >
> > > > On Aug 29, 2006, at 1:13 PM, James Whitehouse
> > wrote:
> > > >
> > > > > Marc,
> > > > >
> > > > > Thanks for that, I'll try cleaning the
> > connector on the radiator-
> > > > > mounted
> > > > > thermo switch first. I don't have any
> > knowledge of anything similar to
> > > > > 'Nolox', but I use DeoxIt as a contact
> cleaner
> > often and it seems
> > > > > to work
> > > > > OK. If that doesn't help, I'll probably try
> > replacing that thermo-
> > > > > switch
> > > > > first, followed by the 'radiator fan 1st
> > speed' relay in the fuse
> > > > > box -
> > > > > they're not expensive parts.
> > > > >
> > > > > If anyone else has any more info/ specs on
> the
> > system, please let
> > > > > me know,
> > > > > I'd be grateful for any fault finding
> > procedures, etc.
> > > > >
> > > > > Cheers,
> > > > > James
> > > > >
> > > > >
> > > > >> -----Original Message-----
> > > > >> From: The CyberPoet
> > [mailto:thecyberpoet at cyberpoet.net]
> > > > >> Sent: 28 August 2006 12:22
> > > > >> To: James Whitehouse
> > > > >> Cc: v6-12v at audifans.com
> > > > >> Subject: Re: [V6-12v] Radiator Fans not
> > switching in correctly...
> > > > >>
> > > > >> This isn't my area of expertise, but I do
> > know that on my V6's (at
> > > > >> least based on my experiences), the
> following
> > seems generally true:
> > > > >>
> > > > >> (A) There are two electrically-driven fans,
> > the primary one triggers
> > > > >> on temp of the radiator temp sensor, and
> the
> > second of which triggers
> > > > >> based on air conditioning use (as well as
> > kicking on at a higher
> > > > >> thermal level threshold for the
> > radiator/engine).
> > > > >>
> > > > >> (B) The wiring connectors for the sensors
> is
> > often the first thing to
> > > > >> go bad, because of exposure in my
> experience.
> > Cleaning the contacts
> > > > >> thoroughly & dielectric grease is often the
> > best place to start.
> > > > >> Sidenote: I've found a dielectric grease
> > called Nolox that contains
> > > > >> zinc particles in the suspension which
> forces
> > a fresh cut through
> > > > >> surface corrosion on connectors every time
> > the plugs are mated works
> > > > >> better than traditional vasoline-like
> > dielectric grease if there is
> > > > >> already a problem with connectivity. There
> > are Brit-market
> > > > >> equivalents (I selected Nolox because all
> the
> > other options were UK-
> > > > >> based and not readily available here). This
> > is not a total solution
> > > > >> for bad connectivity, but given a connector
> > that already had to be
> > > > >> cleaned of surface corrosion once, I'll
> grab
> > the nolox just to
> > > > >> improve the situation in the future (such
> as
> > plugging/unplugging tail
> > > > >> light connectors on the road where I don't
> > carry a full toolkit with
> > > > >> sandpaper, etc. with me)...
> > > > >>
> 
=== message truncated ===