Christoph Bollig

Hi again,

My odometer suddenly stopped working at 191 k km. It never turned the
numbers very smoothly, but always counted accurate enough for my
purposes. It suddenly stopped completely. The speedometer still works
fine.

It's the one which gets an electronic signal, not a turning cable.

I tried to do my homework this time round. What I found so far:

- Most people report a failure of speedo and odo together, which is
due to bad solder joints.

- Some have odometer problems like me.

- I read somewhere, that a plastic gear might have lost a tooth.

However:

I can take the speedometer unit out, but I cannot take it apart. The
main problem is to get the needle off, which is in the way. I cannot
see any damage on any gear, when I look at the complete unit.

If anyone can help me to take it apart, I might get there in the end.

Before I forget, I didn't find the pin outs of the speedometer, so I
figured them out myself. It has two jumper-like connectors, each with
two pins:

Top connector, top pin: positive supply (it says "+15" on the board)
Top connector, bottom pin: ground

Bottom connector, top pin: signal in
Bottom connector, bottom pin: Some voltage out, which is dependent on
speed (Starts at ~10V and decreases with speed to ~7V at 100 km/h).

The signal in just seems to come from a switch which closes to ground
and opens while driving.

But I am still stuck with a broken odometer and don't know how to
proceed. Any ideas are appreciated.

Thanks,

Christoph

P.S. It is a South African Audi 500, which is equivalent to the US and
European Audi100
--
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.

Steve Sears

Christoph,
If you press the reset button on the trip counter _while you are moving_ the
plastic gear which the button is connected to may permanently slide away
from the connecting gears of the odometer/trip meter. If you search in
Audifans you may find the name of the VDO repair facility that can fix the
cluster for you - or how some have used a dab of epoxy glue to repair the
gear. You'll have to disassemble the cluster to get at it, a great time to
replace any burned-out light bulbs in there while-you're-at-it.
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:kfbb90hrqv1ovophjdvhj3808fulduus5a@4ax.com...
> Hi again,
>
> My odometer suddenly stopped working at 191 k km. It never turned the
> numbers very smoothly, but always counted accurate enough for my
> purposes. It suddenly stopped completely. The speedometer still works
> fine.
>
> It's the one which gets an electronic signal, not a turning cable.
>
> I tried to do my homework this time round. What I found so far:
>
> - Most people report a failure of speedo and odo together, which is
> due to bad solder joints.
>
> - Some have odometer problems like me.
>
> - I read somewhere, that a plastic gear might have lost a tooth.
>
> However:
>
> I can take the speedometer unit out, but I cannot take it apart. The
> main problem is to get the needle off, which is in the way. I cannot
> see any damage on any gear, when I look at the complete unit.
>
> If anyone can help me to take it apart, I might get there in the end.
>
> Before I forget, I didn't find the pin outs of the speedometer, so I
> figured them out myself. It has two jumper-like connectors, each with
> two pins:
>
> Top connector, top pin: positive supply (it says "+15" on the board)
> Top connector, bottom pin: ground
>
> Bottom connector, top pin: signal in
> Bottom connector, bottom pin: Some voltage out, which is dependent on
> speed (Starts at ~10V and decreases with speed to ~7V at 100 km/h).
>
> The signal in just seems to come from a switch which closes to ground
> and opens while driving.
>
> But I am still stuck with a broken odometer and don't know how to
> proceed. Any ideas are appreciated.
>
> Thanks,
>
> Christoph
>
> P.S. It is a South African Audi 500, which is equivalent to the US and
> European Audi100
> --
> 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

Hi Steve,

Thanks for your reply. It seems my main problem is still to take the
speedometer itself apart (see below), and there the main problem is to
get the needle off.

> If you press the reset button on the trip counter _while you are moving_ the
> plastic gear which the button is connected to may permanently slide away
> from the connecting gears of the odometer/trip meter.

I have seen that mentioned in a number of places at audifans.com.
However, I was under the impression that this applies more to the
older speedometers, which are driven by a mechanical cable from the
gear box and not by an electronic signal.

It stopped 258km after I last reset the trip counter, no idea whether
I did that while standing or moving slowly.

> If you search in
> Audifans you may find the name of the VDO repair facility that can fix the
> cluster for you -

I life in South Africa, I guess I have to find some other way to find
the right place.

> or how some have used a dab of epoxy glue to repair the
> gear.

Again, I thought that applies to the older ones (pre ~198, which are
driven with the mechanical cable. I also have an Audi 500, 1988, which
I believe is like the American 5k or European Audi 100 pre-facelift.
That one has a more squarish dashboard and the old speedometer with
the mechanical cable. There, I did fix it with a bit of glue.

> You'll have to disassemble the cluster to get at it, a great time to
> replace any burned-out light bulbs in there while-you're-at-it.

I did already take the instrument cluster out and the speedometer of.
I checked all electrical contacts, they seem fine. I have now put the
main instrument cluster back but kept the speedometer out, so that I
can try fix it (or get it fixed).

Ok, I did get a bit further today. I did the following:

1.) I supplied +13 V and ground to the top two pins (the ones which
look like a jumper connection).

2.) I hooked a square wave generator to an oscilloscope and then to
the higher one of the bottom two connector and to ground (the lower
one of the top two). The square wave was set to go from 0 to 7 V.
These were the two values I measured with the Speedometer in the car
when I moved it very slowly.

3.) I turned the frequency of the square wave up and down and the
speedometer needle moves very nicely, but the odometer still doesn't
count. However, the little motor on the board turns. It actually jumps
in steps of 1/10 revolution, i.e. it jumps forward 10 times for one
full turn. It goes faster with a higher frequency, as expected.

Here is what I measured:

- When the speedometer shows 120 km/h, the frequency of the square
wave is 130.5 Hz.

- At this stage, the little motor needs 4.9s for one revolution.

==> 120 km/h is 2 km/min, which is 1km every 30s.
==> The motor does 6.1 revolutions in 30s, I assume it is supposed to
do 6 revoltutions per km. I guess there is a 6 to 1 gear ratio from
the motor to the lowest dial on the km counter.

However, I don't know how acurate my speedometer displays the speed. I
can double-check with a value I found somewhere. Someone stated, that
the there are exactly 6644 signals for 1 mile. This would be 6644 /
1.609 = 4129 signals per km.

At 130.5 Hz, I would then be doing 31.64 m/s or 113.9 km/h (well
possible that the speedometer shows 120 km/h at that speed). If that
is true, I would go 155 m for every revolution of the motor or have
6.45 revolutions per km, which indicates a gear ratio of 13 to 2.

Whichever is true, I can only see that the motor turns and the km
number rings don't. I can see one gear close to the motor, which
doesn't turn either. It looks as if I could get closer to the problem
by taking the board with the motor off. That is srewed on below the
black plate, which is under the speedometer needle. It seems all I
need to do to get in is to take the speedometer needle off. I tried to
pull it quite hard, but I am afraid I might brake something. If anyone
can tell me how to get that needle off, I might be able to do the rest
myself.

Anyway, maybe the numbers above will help someone else at some stage.
If I do manage to take it apart, I will let you know what the problem
was.

Thanks 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.

Steve Sears

Christoph,
You're really getting technical on this fix.....you wouldn't happen to be an
engineer, would you?
Regardless of the method for getting the speed signal to the instrument
cluster, resetting the trip odometer will still result in a gear failure of
the odometer/trip odometer. If the motor turns, but the rings do not, the
problem's got to be in the connection between the two.
I'm pretty sure that the speedo needle is pressed on to the shaft:
Problem with electronic system:
http://www.audifans.com/archives/1998/11/msg03712.html
Use a screwdriver to remove needle:
http://www.audifans.com/archives/1998/11/msg03756.html
And hey, to find out about removing the needle - look no further than the
land of posting in the subject line:
http://www.audiworld.com/tech/pix/face8.jpg - of course, they're removing
the needles to change the colour of the gauge face, not fix anything that's
broken.
http://www.mnsi.net/~natwhite/Audi/I...entcluster.htm - here's your best
bet.
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:5cli90lodlgi91hjh3jjdf64bcnb76svc0@4ax.com...
> Hi Steve,
>
> Thanks for your reply. It seems my main problem is still to take the
> speedometer itself apart (see below), and there the main problem is to
> get the needle off.
>
> > If you press the reset button on the trip counter _while you are moving_
the
> > plastic gear which the button is connected to may permanently slide away
> > from the connecting gears of the odometer/trip meter.
>
> I have seen that mentioned in a number of places at audifans.com.
> However, I was under the impression that this applies more to the
> older speedometers, which are driven by a mechanical cable from the
> gear box and not by an electronic signal.
>
> It stopped 258km after I last reset the trip counter, no idea whether
> I did that while standing or moving slowly.
>
> > If you search in
> > Audifans you may find the name of the VDO repair facility that can fix
the
> > cluster for you -
>
> I life in South Africa, I guess I have to find some other way to find
> the right place.
>
> > or how some have used a dab of epoxy glue to repair the
> > gear.
>
> Again, I thought that applies to the older ones (pre ~198, which are
> driven with the mechanical cable. I also have an Audi 500, 1988, which
> I believe is like the American 5k or European Audi 100 pre-facelift.
> That one has a more squarish dashboard and the old speedometer with
> the mechanical cable. There, I did fix it with a bit of glue.
>
> > You'll have to disassemble the cluster to get at it, a great time to
> > replace any burned-out light bulbs in there while-you're-at-it.
>
> I did already take the instrument cluster out and the speedometer of.
> I checked all electrical contacts, they seem fine. I have now put the
> main instrument cluster back but kept the speedometer out, so that I
> can try fix it (or get it fixed).
>
> Ok, I did get a bit further today. I did the following:
>
> 1.) I supplied +13 V and ground to the top two pins (the ones which
> look like a jumper connection).
>
> 2.) I hooked a square wave generator to an oscilloscope and then to
> the higher one of the bottom two connector and to ground (the lower
> one of the top two). The square wave was set to go from 0 to 7 V.
> These were the two values I measured with the Speedometer in the car
> when I moved it very slowly.
>
> 3.) I turned the frequency of the square wave up and down and the
> speedometer needle moves very nicely, but the odometer still doesn't
> count. However, the little motor on the board turns. It actually jumps
> in steps of 1/10 revolution, i.e. it jumps forward 10 times for one
> full turn. It goes faster with a higher frequency, as expected.
>
> Here is what I measured:
>
> - When the speedometer shows 120 km/h, the frequency of the square
> wave is 130.5 Hz.
>
> - At this stage, the little motor needs 4.9s for one revolution.
>
> ==> 120 km/h is 2 km/min, which is 1km every 30s.
> ==> The motor does 6.1 revolutions in 30s, I assume it is supposed to
> do 6 revoltutions per km. I guess there is a 6 to 1 gear ratio from
> the motor to the lowest dial on the km counter.
>
> However, I don't know how acurate my speedometer displays the speed. I
> can double-check with a value I found somewhere. Someone stated, that
> the there are exactly 6644 signals for 1 mile. This would be 6644 /
> 1.609 = 4129 signals per km.
>
> At 130.5 Hz, I would then be doing 31.64 m/s or 113.9 km/h (well
> possible that the speedometer shows 120 km/h at that speed). If that
> is true, I would go 155 m for every revolution of the motor or have
> 6.45 revolutions per km, which indicates a gear ratio of 13 to 2.
>
> Whichever is true, I can only see that the motor turns and the km
> number rings don't. I can see one gear close to the motor, which
> doesn't turn either. It looks as if I could get closer to the problem
> by taking the board with the motor off. That is srewed on below the
> black plate, which is under the speedometer needle. It seems all I
> need to do to get in is to take the speedometer needle off. I tried to
> pull it quite hard, but I am afraid I might brake something. If anyone
> can tell me how to get that needle off, I might be able to do the rest
> myself.
>
> Anyway, maybe the numbers above will help someone else at some stage.
> If I do manage to take it apart, I will let you know what the problem
> was.
>
> Thanks 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.