type 89 speedo data information?

Huw Powell audi at humanspeakers.com
Thu Jan 25 16:23:14 EST 2007

> I have two busted odometers, and want to try to fix one "on the bench", 
> which would mean needing to synthesize the data stream from the sender 
> in order to see if I've succeeded.

The report so far... good news and bad news.

My new gear arrived today, so I did the minimal reassembly to test it 
out (inserting gears, screwing motor/PCB assembly back to side of 
speedo/odo body).  Upon applying power and my 200 Hz signal, the 
odometer is happily clicking away.  So that certainly the right part and 
the right fix for the busted odometer.

Here's the problem - the speedometer (I put the needle back on to test 
it as well before further reassembly, a neurosis of mine, to test at 
every step...) is not reacting.  I've done some measurements and 
testing, making it seem even odder.

Speedo coil measures about 90 ohms.  Voltage to it at 200 Hz (about 100 
mph) reads just under 3 volts.  With all disconnected, applying 3 volts 
to it makes the needle jump just as it should, although there is no 
"sprung" return.  In other words, applying the same voltage that is 
present during "frequency" testing creates a result not present during 
that frequency testing.

Wondering if I managed to either fry some little component on the PCB 
(if so, why is that voltage present?), or gum up the works of the 
coil/needle assembly.

I doubt there is any btdt out there, but I'm asking anyway...

Next step is to pull my other speedo/odo and see if I can fix that one 
instead.  Without breaking it.

Huw Powell



More information about the quattro mailing list