Diesel to Gas Gauge Cluster Swap: Possible?

Unfortunately, my instrument cluster (total failure of the indicator displays in a Passat TDI estate, first registered 12/95, 66kW, 1.9L, chassis number: 0600) is still defective, my post regarding repair tips was not very successful, and replacements seem to be scarce on eBay and similar platforms. Therefore, I'm considering the following:

Can I easily connect a keyless entry system from a gasoline-powered car? There are plenty of them available.

Suitable for license plate codes AUS, ADY, and AGG. Speedometer up to 240 km/h. Manufacturer: MotoMeter. Used in GTI and 16V models from 1994 to 1997. Part number: 3A0 919 860 GX (I do not have this part; the information comes from an online marketplace and is only an example).
The only (visual) difference is the higher speedometer reading (over 220), as well as the higher maximum RPM, including the red zone.
Unfortunately, I don't know if the power source for the tachometer is the same as the one for the other instruments, and I'm not sure if the connector even fits.
Has anyone ever installed/tested this before?
I would be very grateful for any answers and tips.

Greetings, friend.

Just a note: 0600 is just the manufacturer code (VW). If anything, zu3 would be interesting.

I can tell you about my experience with my Audi: the tachometer signal wasn't a problem at all. There was a sticker on the back of the tachometer unit indicating how many pulses corresponded to a kilometer. In both cases, it was 4280 pulses per kilometer. My old instrument cluster didn't have a tachometer, but there was still a tachometer signal present. Unfortunately, the instrument cluster from the gasoline-powered car already showed values between 3000 and 4000 RPM at idle, depending on the position of the potentiometer (used for calibrating the tachometer). This was probably exactly four times the number of pulses. I had already designed a circuit that would use two frequency dividers (J-K flip-flops) to divide the pulses by four, but the BMW I collided with intervened before I could implement it.

Hello friend.

"I have a KI (instrument cluster) from a gasoline-powered car installed in my diesel vehicle, with an onboard computer. Everything works fine, except for the glow plug indicator, which you'll need to retrofit. However, you'll have to accept the very faint glow of the glow plug indicator. The KI from the gasoline car is wired differently internally, which is why it glows. The function is otherwise okay. Pay attention to the manufacturer; if you're switching from Motometer to VDO, you may need to add an additional ground wire to the speedometer cable harness. The tachometer works perfectly."

Hi Benno,

First of all, thank you both, mahk and Benno.

'...you just need to add the preheating indicator...'
'I hadn't even thought about that! But it makes sense, it's not necessary for a gasoline engine. Do I really need it, Benno? In other words, I haven't really paid attention to it so far; I turn the key further out of habit after a few 'momentary pauses'.'
And what do you understand by 'retrofitting'? Do I just need to solder a (yellow) LED onto the circuit board at a designated location, meaning that solder pads are already present on the board, or do I also need to solder in the appropriate resistor (SMD)?
My AI unit is, incidentally, without MFA (Multi-Function Display) and is from MotoMeter. The one you installed has MFA. By the way, would that mean I could also connect a gasoline-powered AI unit with MFA?
Important information: Does the existing connector fit into the fuel injection control unit (FIU)? If so, does it fit both versions, with and without the Multifunction Display (MFA)? Otherwise, I'm quite concerned about my conversion project because I absolutely don't have any wiring diagrams with the connector pinouts to create an adapter cable.
Sorry, Benno, if I bombard you with a bunch of questions right away. But since you are a 'knowledgeable' person, you have to make use of it .

Greetings, friend.

You can integrate an AI system with MFA (Multi-Function Display), but if you want to use the MFA's functions, you will also need the steering column lever and the sensors (outside temperature, oil temperature), and you may need to integrate some cables into the wiring harness.

Best regards, WarLord.

Hello WarLord, thanks for the information. However, the effort involved would be too much for me. So, I would implement it without the MFA (Multi-Factor Authentication) function.
Here's another question for Benno, and he writes:
...Pay attention to the manufacturer; if you are switching from Motometer to VDO, you may need to add an additional ground wire to the speedometer wiring harness.
Where, at which pin, do I need to connect an additional ground ? My instrument cluster is from MotoMeter, while eb... offers several, but those are from VDO.
Thank you for your help.
Greetings, friend.

Hello friend.

Feel free to buy a VDO instrument cluster. Just try it out, because many wiring harnesses have a second ground connection. It's best to remove the glow plug LED from the old instrument cluster and install it in the new one. You don't need to change anything else. The flickering comes from the different internal wiring. In the diesel instrument cluster, the LED is directly connected to ground, while in the gasoline instrument cluster, the connection goes to an IC. However, this is only noticeable in the dark.

Best regards, Benno.

... The glow comes from the other internal wiring. In the diesel speedometer, the LED is directly connected to ground, while in the gasoline speedometer, the connection goes to an IC. However, this is only noticeable in the dark...

Greetings, Benno.

Aha, I initially understood that instead of a bright glow (during the preheating process), only a faint glimmer would be visible. Now everything is clear, and the LED installation is straightforward. Thanks to a hint I found on this forum in another section, I downloaded the electrical diagram for the Passat from a Russian website, but unfortunately, the quality is not good; in some parts, you can only guess what it means.

Benno, there's one more thing I'd like to know:
Currently, VR6 offers many affordable instrument clusters (apparently VDO brand). However, I suspect I might encounter problems with the correct display of the tachometer during installation, as the VR6 has more cylinders than my 90hp TDI. Or is this instrument cluster also usable without any issues?

Greetings, friend.

Hello friend.
I only just found the link to become a "Blaumann" today. I didn't know that you have to be "blue" to write in this forum.
You can't use the tachometer from a VR6 engine in this application, as it will display an incorrect reading.
I hope I was able to help you.

Best regards, Benno.

I have personally swapped MotoMeter and VDO units before, and it worked without any problems (due to the grounding issue).
It's generally possible to swap the combination instrument cluster from a gasoline engine to a diesel engine, or vice versa, unless it's a TDI. In that case, the tachometer signals are different.

It's important that the number of cylinders is correct, which is why the VR6 speedometer won't fit.

...I also had to overcome the hurdle of getting the 'blue badge.' I was initially surprised that I suddenly couldn't write anything, even though I had the correct password, but '-those who can read have an advantage-' it took me a while to understand what the error message was saying...
Hello Benno and Golfosaurus,
I had already suspected that there might be variations in the firing order of a 6-cylinder engine, but I wasn't sure. It might be possible to influence the timing ratio by bridging a solder joint or something similar, but that would probably only be known to experts at the manufacturer or service department.
Okay, thank you all, so I'll try to find a cheap AI (artificial intelligence) system from a gasoline-powered car so I can finally see how much diesel I have left in the tank, not to mention everything else...

Greetings, friend.

There are no solder bridges or anything like that; it's hardcoded in the AI's memory. You can display the setting, but you can't change it.
It might be possible that people could do that (after all, it's possible to manipulate speedometers, so it's possible to "tinker" with the memory), but I'm not aware of any such cases.

However, with certain AI models, specifically those of the G4 generation, the number of cylinders can be adjusted via OBD.

@amigo

Hm, since you're writing about repair tips: What did you get?

Best regards, WarLord.

@amigo

Hm, since you're writing about repair tips: What did you get?

Greetings, WarLord.

Hello WarLord.
The main suggestion was to check the soldering around the connector area. Unfortunately, that didn't help. Here's the link; I hope it's allowed and that it works.
/viewtopic.php?t=8435&highlight=

Unfortunately, even using a magnifying glass to inspect the circuit board was not successful, as some areas were partially obscured. Moreover, a hairline crack would be difficult to detect with a magnifying glass, and if it's a multilayer circuit board, there would be no way to visually identify any interruptions.
Reworking the entire circuit board would be extremely time-consuming, as many components would first need to be removed so that the rest of the board could be run through the reflow soldering machine and the SMD components could be resoldered. It is also possible to resolder the SMD components by hand, which I have done thousands of times, but reworking a complete circuit board is quite challenging, especially since there's no guarantee that it will then function correctly.

However, since the complete analog gauges are malfunctioning, while everything else seems to be working, and the needles appeared to accelerate towards the full scale before failing, I suspect a component on the circuit board has failed. Without a schematic, it's almost impossible to diagnose, as the board is too complex.
Well, asking doesn't cost anything, and it was definitely worth a try.

Once again, thank you to everyone involved.
Greetings, friend.

I seem to recall something about voltage regulators, that they sometimes fail or have cold solder joints.

Check out www.35i-forum.de; there's definitely information to be found there.

Best regards, WarLord.

I seem to recall something about voltage regulators, that they sometimes fail or have cold solder joints.

Check out www.35i-forum.de; there's definitely information to be found there.

Greetings, WarLord.

Hello WarLord, the AI units discussed there appear to be from an older generation and have different circuit boards, at least the ones I've found. Therefore, they are not very useful.

I ended up buying and installing a gasoline-powered control unit. So far, it's working fine. I haven't retrofitted the preheating LED yet, but maybe I'll do that later, if I'm bored.

However, I did notice something (negative): the fuel gauge is showing too much!
To be sure, I filled the tank completely. Conclusion: The gauge showed a good reading (indicating over 60 liters) before filling. After filling completely, it showed 70 liters. This is fine, unless almost 21 liters were actually added. The gauge should have been somewhere around the 50-liter mark. At least, the gauge with the old instrument cluster was very accurate.
It might still be within the acceptable range, has anyone had experience with this? Perhaps the resistance values of the sensors (gasoline/diesel) are different; does anyone know?
It's not that bad, as long as the display works better when it's showing the 'empty' direction. It would be really awful to eventually be standing there with a 20-liter fuel gauge reading and still have an empty tank.
Is there a way to adjust it, perhaps through programming by the developers? In the wiring diagram (from the Russian URL, which is partially difficult to read), I haven't found anything that appears to be 'electrically rotatable.'

Greetings, friend.