Hi everyone,

This morning I encountered something strange:

When I switched on the heater fan, it ran but relatively slowly. Even
at full speed it was just about noticable. Normally, it is strong and
loud at maximum speed.

I didn't think much about it until I went at some speed around a
corner, and suddenly it was strong for a second or two. I tried a few
more things:

- When I turn left fast enough, it goes strong for a second or two

- When I turn right, nothing changes

- When I brake or accelarate, also nothing happens

It remained a bit stronger after going through a few corners, but
still not at full power.

I know the connections could be bad in quite a few places, but if
anyone has any idea where to look first, I would appreciate it.

Before I forget: It's a South African (left-hand drive, steering on
the right) Audi 500, 1988, which is equivalent to the American
Audi 5k or European Audi 100.

Thanks,

Christoph
--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.

 

Three possibilities:
(1) a loose electrical connection that is being strained by centrifugal
force while cornering.
(2) debris close to the fan blades that starts to make contact during
cornering,
(3) a bad fan bearing.


On Wed, 21 Apr 2004 10:29:12 +0200, Christoph Bollig <laserpower@gmx.net>
wrote:

> Hi everyone,
>
> This morning I encountered something strange:
>
> When I switched on the heater fan, it ran but relatively slowly. Even
> at full speed it was just about noticable. Normally, it is strong and
> loud at maximum speed.
>
> I didn't think much about it until I went at some speed around a
> corner, and suddenly it was strong for a second or two. I tried a few
> more things:
>
> - When I turn left fast enough, it goes strong for a second or two
>
> - When I turn right, nothing changes
>
> - When I brake or accelarate, also nothing happens
>
> It remained a bit stronger after going through a few corners, but
> still not at full power.
>
> I know the connections could be bad in quite a few places, but if
> anyone has any idea where to look first, I would appreciate it.
>
> Before I forget: It's a South African (left-hand drive, steering on
> the right) Audi 500, 1988, which is equivalent to the American
> Audi 5k or European Audi 100.
>
> Thanks,
>
> Christoph

 

Jay Somerset <jay@H0TMAIL.com> wrote in message news:<inic809e361q3cec3cpdrns7l54fest56i@4ax.com>. ..
> Three possibilities:
> (1) a loose electrical connection that is being strained by centrifugal
> force while cornering.
> (2) debris close to the fan blades that starts to make contact during
> cornering,
> (3) a bad fan bearing.

Most likely the last of the three.
--
C.R. Krieger
(Had a 2002 that did it. No; not a new Audi; an *old* BMW.)

 

Hi Jay and C.R.

Thanks for your replies.

On 21 Apr 2004 07:48:42 -0700, (C.R. Krieger) wrote:
> Jay Somerset <jay@H0TMAIL.com> wrote in message news:<inic809e361q3cec3cpdrns7l54fest56i@4ax.com>. ..
> > Three possibilities:
> > (1) a loose electrical connection that is being strained by centrifugal
> > force while cornering.
> > (2) debris close to the fan blades that starts to make contact during
> > cornering,
> > (3) a bad fan bearing.
>
> Most likely the last of the three.

What makes you think it's that?

It seemed to be more of a jump between high and low speeds, that's why
I thought it would be a bad electrical contact and was mainly
wondering where best to start to look for it.

I don't think it's (2), since I don't here any excessive noise when it
goes slow. It makes more of a noise when it is blowing stronger, and
that noise is the same it always made when it was running on full
speed.

Thanks,

Christoph

--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.

 

"Christoph Bollig" <laserpower@gmx.net> wrote in message
news:0m6d80dg8j6or9pl4in864hprihfaq33nb@4ax.com...
> Hi Jay and C.R.
>
> Thanks for your replies.
>
> On 21 Apr 2004 07:48:42 -0700, (C.R. Krieger) wrote:
> > Jay Somerset <jay@H0TMAIL.com> wrote in message
news:<inic809e361q3cec3cpdrns7l54fest56i@4ax.com>. ..
> > > Three possibilities:
> > > (1) a loose electrical connection that is being strained by
centrifugal
> > > force while cornering.
> > > (2) debris close to the fan blades that starts to make contact during
> > > cornering,
> > > (3) a bad fan bearing.
> >
> > Most likely the last of the three.
>
> What makes you think it's that?
>
> It seemed to be more of a jump between high and low speeds, that's why
> I thought it would be a bad electrical contact and was mainly
> wondering where best to start to look for it.
>
> I don't think it's (2), since I don't here any excessive noise when it
> goes slow. It makes more of a noise when it is blowing stronger, and
> that noise is the same it always made when it was running on full
> speed.
>
> Thanks,
>
> Christoph




Christoph.
I had exactly the same symptoms, 1989 Audi 100 UK, removed the fan and
discovered.........

Badly worn commutator & brushes to such an extent that there was a deep
trapezoidal groove in the commutator.
Remaining brush length was very short such that the brushes barely touched
the commutator during straight line motoring. Hence slow speed running.
However, on cornering, the end float in the motor allowed its armature to
move axially. (The motor is mounted transversely in the engine compartment )
This in turn allowed the commutator & brushes to make better contact albeit
on the sides of the worn groove in the commutator.

imagine a longitudinal cross section as below ...

brush ===)) comm. ((===brush

As the condition really deteriorates. No contact between commutator &
brushes. No motor rotation
Commutator moves vertically (in this pictorial representation ) during
cornering allowing contact to be made. Motor runs.

I had to replace the motor as the commutator really was too worn to skim.
Quite an awkward job to remove it. Motor cost about £60 GB from one of the
European car part suppliers 2 or 3 years ago.

I have a vague recollection that there is some rubber pipework to either
cool or extract dust from the commutator end of the motor, or grommets in
that vicinity. Removal of this/these may allow visual inspection of the
commutator. Alternatively you may find a way of applying an axial force to
the motor to test the theory.

Good Luck !
Ian

 

Christoph,
Yep, worn brushes and commutator on the fan motor. (BTW, excellent ASCII
art Ian)
The repair - although developed for 5k's in the US although it may be
similar in RHD cars as well:
http://www.audifans.com/archives/1996/07/msg01363.html
Note the author's revisions - you can find this and other postings on the
subject by searching Audifans archive for "steak knife"
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)

 

On Wed, 21 Apr 2004 14:46:37 -0400, "Steve Sears"
<steve.sears@SHOESsoil-mat.on.ca> wrote:

> Christoph,
> Yep, worn brushes and commutator on the fan motor. (BTW, excellent ASCII
> art Ian)
> The repair - although developed for 5k's in the US although it may be
> similar in RHD cars as well:
> http://www.audifans.com/archives/1996/07/msg01363.html
> Note the author's revisions - you can find this and other postings on the
> subject by searching Audifans archive for "steak knife"
> Cheers!
> Steve Sears
> 1987 Audi 5kTQ
> 1980 Audi 5k
> 1962 and '64 Auto Union DKW Junior deLuxes
> (SPAM Blocker NOTE: Remove SHOES to reply)
>

Hi Ian and Steve,

Thanks a lot for your help (and the artistic drawing). It sounds like
a bit of a job, but I am quite sure that the diagnosis is right.

Just to make sure that the problem is in the blower motor and not
anywhere in the electrical contacts, I would like to check the voltage
into the motor. Is there any information available on the voltages the
blower moter should get at the different speed settings?

Thanks again,

Christoph
--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.

 

Christoph,
Maybe in the Bentley -
Have you searched the Audifans site? (I did some free work for you if you
didn't):
http://www.audifans.com/archives/1998/02/msg02596.html
http://www.audifans.com/archives/1998/07/msg02901.html
http://www.audifans.com/archives/1995/01/msg00134.html
or how about Scott Mockry's web site:
http://www.sjmautotechnik.com/TROUBLE_SHOOTING/AC.html
There ya go.
Cheers!
Steve Sears
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
(SPAM Blocker NOTE: Remove SHOES to reply)

"Christoph Bollig" <laserpower@gmx.net> wrote in message
news:qfff80h7qgi2rj2id6srge4j268rjj180i@4ax.com...
> On Wed, 21 Apr 2004 14:46:37 -0400, "Steve Sears"
> <steve.sears@SHOESsoil-mat.on.ca> wrote:
>
> > Christoph,
> > Yep, worn brushes and commutator on the fan motor. (BTW, excellent
ASCII
> > art Ian)
> > The repair - although developed for 5k's in the US although it may be
> > similar in RHD cars as well:
> > http://www.audifans.com/archives/1996/07/msg01363.html
> > Note the author's revisions - you can find this and other postings on
the
> > subject by searching Audifans archive for "steak knife"
> > Cheers!
> > Steve Sears
> > 1987 Audi 5kTQ
> > 1980 Audi 5k
> > 1962 and '64 Auto Union DKW Junior deLuxes
> > (SPAM Blocker NOTE: Remove SHOES to reply)
> >
>
> Hi Ian and Steve,
>
> Thanks a lot for your help (and the artistic drawing). It sounds like
> a bit of a job, but I am quite sure that the diagnosis is right.
>
> Just to make sure that the problem is in the blower motor and not
> anywhere in the electrical contacts, I would like to check the voltage
> into the motor. Is there any information available on the voltages the
> blower moter should get at the different speed settings?
>
> Thanks again,
>
> Christoph
> --
> Important: Emails sent to me which contain my full name
> in the "to:" or "cc:" field will bypass my spam filter.
> With most programs "Reply" should do the job.

 

The brushes are the problem - for sure.

If you want to do an easy test, remove plastic cover to gain access to
blower housing. On the passenger side (of your car) of the blower
housing there is a rubber elbow. Remove it and the brushes are directly
visible. Use a wooden dowel or other non-conductor to lightly touch the
brushes when they have power. This will alter the contact and make the
motor run fast for a bit.

Your motor will quite completely within a month or so.

Tony

'91 100q 5spd
fourth type 44
(have changed blower motors for this in two of my cars and a number of
friends cars.)

Christoph Bollig wrote:
> On Wed, 21 Apr 2004 14:46:37 -0400, "Steve Sears"
> <steve.sears@SHOESsoil-mat.on.ca> wrote:
>
>
>>Christoph,
>>Yep, worn brushes and commutator on the fan motor. (BTW, excellent ASCII
>>art Ian)
>>The repair - although developed for 5k's in the US although it may be
>>similar in RHD cars as well:
>>http://www.audifans.com/archives/1996/07/msg01363.html
>>Note the author's revisions - you can find this and other postings on the
>>subject by searching Audifans archive for "steak knife"
>>Cheers!
>>Steve Sears
>>1987 Audi 5kTQ
>>1980 Audi 5k
>>1962 and '64 Auto Union DKW Junior deLuxes
>>(SPAM Blocker NOTE: Remove SHOES to reply)
>>
>
>
> Hi Ian and Steve,
>
> Thanks a lot for your help (and the artistic drawing). It sounds like
> a bit of a job, but I am quite sure that the diagnosis is right.
>
> Just to make sure that the problem is in the blower motor and not
> anywhere in the electrical contacts, I would like to check the voltage
> into the motor. Is there any information available on the voltages the
> blower moter should get at the different speed settings?
>
> Thanks again,
>
> Christoph

 

Hi Tony, Steve and Ian,

It's blowing like never before

> The brushes are the problem - for sure.

Thanks again for the advice. I opened it up, and didn't waste any time
on electrical connections or anything else. You were right, the
brushes are the problem.

> If you want to do an easy test, remove plastic cover to gain access to
> blower housing. On the passenger side (of your car) of the blower
> housing there is a rubber elbow.

That was the first surprise I came across: no rubber elbow despite the
fact that everyone mentions it. And some yellow dots on the blower
moter. I've only got the car since three years and someone must have
replaced the motor before with one from the scrapyard (they tend to
put yellow paint on to identify their items). The rubber elbow was
missing completely, I don't know whether that's a problem.

> Remove it and the brushes are directly visible.

Saw them and even tried to take some photos. If I ever get round, I
might write a short text. Is anyone interested to put it on a web
page?

> Use a wooden dowel or other non-conductor to lightly touch the
> brushes when they have power. This will alter the contact and make the
> motor run fast for a bit.

Even a slight wobble on the cable made a difference. Then, I sprayed a
bit of contact cleaner into it, and that made it run faster for a few
seconds as well.

The commutator looked fine to me (no groove). It just seemed that the
brushes were not touching any more. Their travel seems to be limited
by the holder and the cable hitting the end of the holder. I unplugged
the motor and used a small screwdriver to bend the holder down. A bit
more contact spray and it now runs very smooth.

> Your motor will quite completely within a month or so.

I hope I got a bit more time left (at least get me through our
winter). I would like to find some replacement brushes. I didn't ring
the dealer yet, but I am almost certain they don't sell them
separately. Anyway, next time I go past, I will ask.

Thanks again for your help,

Christoph
--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.