Audi 80 Typ89: Speedometer Signal Source

"This might be a silly question, but does anyone know how my Type 89 gets its speed information? The background is that the daily mileage counter is intermittently failing (after a thorough "reset," it usually works again), and recently, the speedometer has completely stopped working. So far, it's taken anywhere from 5 minutes to a good hour for the speedometer to start working again. Interestingly, after the speedometer starts working again, it initially stops working again in acceleration mode, and only reacts when I press the gas pedal. It sounds like a loose or worn-out connector, which I would expect given the age of the car."

I found these two threads, but they refer to TDIs with all this modern stuff like engine control units , which I don't have.

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

"But the speedometer is definitely electronic, because when I turn off the engine before the gate or somewhere like that, I also lose the speedometer signal."

"Perhaps you could answer another question: How much effort would it be to retrofit a tachometer? And is it even possible? The alternator definitely has a W-terminal, but it's very difficult to find tachometers for that model year. And the newer ones are all from the B4, which are most likely TDI tachometers, and those probably won't display anything without a coolant temperature sensor."

The AAZ engine was still available in the B4 model.

It also had the crooked double pipes, but it's a mechanically driven vortex chamber tractor.

If the Lima translation is a good fit for the KW (keywords), then that would be exactly the candidate we're looking for.

m;

Regarding the instrument cluster: It is possible to retrofit it, and there was also a factory-installed version for the Type 89 TD. Take a look here, the second post from the bottom. In principle, you can mix individual B4 and 89 instrument cluster parts, but they must be from the same manufacturer (Nippon-Seiki or VDO; the B4 had both, the 89s are IMO VDO). Replacing the entire B4 instrument cluster with an 89 instrument cluster is not advisable, as the speedometer will then be inaccurate (different rolling circumference). Furthermore, the B4 has the dynamic oil pressure control and the warning buzzer integrated into the instrument cluster, while in the 89, both are located in the auxiliary relay holder.
However, I doubt that more than a handful of B4-AAZ models were built with a DZM engine.

Regards,
0588.778

Hi,

How about converting a gasoline engine tachometer? They should be much more common (if they can be fitted into your instrument cluster). You would need to "simulate" the ignition pulses electrically, but that should be possible using a Hall sensor or the alternator signal. The only potentially complex part is the frequency multiplication (depending on how many pulses per revolution the tachometer requires), but that can certainly be soldered together.

Best regards,

Jan.

Hello,

Based on my experience searching for a used transmission for a 1990s Audi 100 (which had the same transmissions as the Type 89), there are transmissions with a mechanical speedometer drive (worm gear) and others with an electric pulse generator. This pulse generator is located exactly where the speedometer drive with its worm gear would normally be.

If my memory serves me correctly, the mechanical tachometers were used up to model year 1985 or 1986 in the 100 model, so perhaps only the electric ones are suitable for the Type 89.

Regards,
Martha.

Jan6K wrote:

The only potentially complex part is the frequency multiplication that might be necessary (depending on how many pulses per revolution the tachometer requires), but that can certainly be soldered together.

What does "aufwändig" mean in this case?
Basically, there should be 2 pulses per revolution (something I've always been curious about: what does a crankshaft look like in a 5-cylinder engine?). Do you have a general DIY guide somewhere online? I wouldn't call myself an electronics expert, but I'm pretty good with a soldering iron.

Does anyone know if the gasoline-powered DZM (digital tachometer) actually needs ignition pulses, or if the control unit also outputs a voltage of 0-12V or something similar for the speed signal (and would therefore be satisfied with the W-terminal)?

Uh, I'm just reading a thread on the Mecki forum... apparently, it shouldn't be a problem. And finding a speedometer like that should be possible. I'll check with my usual junkyard... if that doesn't work, I'll just get one from eBay.

Hi,

I don't have any instructions, but I think there's probably something online about it. Frequency converters are a common topic for all sorts of things.

Best regards,

Jan.

I've seen some unusual odometer readings before!

I just re-soldered a circuit board for a friend's odometer today, and now it's working again. One of the pins on the stepper motor had a cold solder joint, which isn't surprising considering the hole was much larger than the pin itself.

I know someone else who has the same problem, so it seems to be quite common.

I managed to get a speedometer from a scrapped car with a 1.8-liter gasoline engine. Unlike my old one, this one is from Nippon Seiki (it has "UN4" on the front). It seems the counter is somehow better; it spins much more smoothly. Or maybe my old one was just completely broken.

Regarding the tachometer: When idling, it already shows between 3000 and 4000 revolutions per minute, depending on the potentiometer position. When I press the accelerator, it seems like the signal is being quartered, rather than just being shifted down by 3000 revolutions. I'll keep an eye out for a diesel-specific tachometer, otherwise, I'll look for a frequency divider circuit and see if I can make it work.

You could definitely make a nice bedside clock out of an old AI device, right? It could be subtly illuminated with a reddish glow, and even be dimmable.

The odometer in VDO instruments always increments in steps because they use a stepper motor. I haven't disassembled any Nippon Seiki odometers yet.

In my DIY book, it states that the B4 TDI engine's tachometer receives its signal from the W-terminal. (Well, DIY books often contain all sorts of information...)
It's possible that the signal is already present in the AI (artificial intelligence) system, and you just need to swap the clock with the tachometer.

The idea with the clock is certainly a nice one .

Certainly, originally the ECU receives the signal from the "W" terminal. When I replaced the ignition coil and the green wire wasn't yet connected to the "W" terminal, I also experienced some interesting effects with the dynamic oil pressure control. Therefore, even an ECU without a tachometer must "know" the engine speed.

I hope that my oil pressure sensor is still working; so far, I haven't noticed any oil leakage. When preheating and shortly after starting, the oil pressure light comes on, then goes off, and there's no alarm even at higher RPMs. I think I'll disconnect the 2-bar pressure sensor and see when it starts to malfunction. If that works, everything should be okay...

mahk wrote:

No question, initially the AI will definitely receive the signal from the W-terminal.

No, it's not necessarily true that an AI has a speed signal. See:

0588.778 wrote:

Furthermore, the B4 incorporates the dynamic oil pressure control and the warning buzzer into the instrument cluster (IC), while in the 89, both are located in the auxiliary relay carrier.

I just wanted to point out that it seems you can actually use a TDI tachometer.

If that helps:

The tachometers in the Audi 80 B4 are interchangeable between the TDI models and the 4/5-cylinder gasoline engines. There are no differences, only different measurement ranges.
The six-cylinder tachometer is not working correctly.

I'm not sure to what extent this applies to the Type 89.

Jan6K wrote:

Hi, How about retrofitting a gasoline engine tachometer? They should be much more common (if they can be installed in your instrument cluster). You would need to "simulate" the ignition pulses electrically, but that should be possible using a Hall sensor or the alternator signal. The only potentially complex part is the frequency multiplication (depending on how many pulses per revolution the tachometer requires), but that can certainly be soldered together. Best regards, Jan

The secret is a J-K flip-flop (thanks to the first semester of digital technology). When you apply a signal to the clock input and set the inputs to a constant high level, it flips Q and Q' with each clock cycle. Therefore, you have exactly half the clock frequency at each of the two outputs. And in my case, it looks like a quarter of the frequency, so the whole thing is happening twice in a row.

now, I have another idea that I think is even funnier: you could probably also fit your digital LDA into the slot for the digital clock.

Hi,

Well, there you go, I knew you could adapt it using fairly simple methods.

Quote:

Here's a thought: wouldn't it be funny if you could also fit your digital LDA into the slot where the digital clock usually goes?

If you can find a suitable panel meter, that's great. Just make sure it's one that can handle the situation where the operating voltage and the measured voltage are connected to the same ground (especially the cheaper ones often can't).

Best regards,

Jan.