Glow Plug Not Working: VW Passat 35i Fix

Hello!
Can you help me?
I'm having the following problem with my Passat 35i B4, 110 HP TDI, manufactured in October 1994...
After my engine swap, replacing the 1Z with an AFN, I still had a few...
Minor electrical issues. I have the efh's from the front, and the e-mirrors.
including the complete wiring harness throughout the car and the installation of the WFS system.
After that, my fuel gauge and interior lights started working again.
no sunroof (donor vehicle without sunroof).
After a long search, I discovered that a pipe is connected to...
Fuel sensor and a ground wire to the sunroof located elsewhere.
The fuse box was already there. I modified it as needed.
It was working the way it used to. Now, everything is working again.
The only problem that remains is the correct display of [something].
Water temperature (approximately 80 degrees Celsius) and a glowing preheating lamp.
It doesn't even light up when I check the temperature sensor in the engine compartment.
abziehe und dann Starte. Vorglühen funktioniert soweit. Only the.
The preheating lamp is constantly glowing, but this is only noticeable in the dark.
Can someone help me with this? Is something missing here?
Combination instrument or control unit?

Kann mir da keiner einen Tipp geben was das sein könnte? I'm really at a loss.
Sure, here is the translation of the text from German to English:

"MFG" is an abbreviation for "Mit freundlichen Grüßen," which means "Sincerely" or "Best regards" in English.

If you can also tell us which vehicle (make and model + year) the AFN engine with its wiring harness came from, we'll be one step closer. (The AFN engine wasn't available in the Passat model year 1995, after all).

Außerdem wäre wichtig, wo du den Kabelbaum überall getauscht hast. Innenraum hast du schon erzählt, aber was ist mit dem zum MSG? OdeSure, here is the translation of the text from German to English:

"r dem zum KI?"
"What is the connection to AI?"

Regards,
Guste.

Hello!
First of all, thank you for your quick response.
Okay, the engine is from a 1996 Passat 35i Facelift B4. The engine wiring harness hasn't been replaced. I was told that it's the same one. According to VW's AKTE parts catalog, it also has the same part number.
Sure, here is the translation of the text from German to English:

"MFG" is an abbreviation for "Mit freundlichen Grüßen," which means "Sincerely" or "Best regards" in English.

Hi,

Unfortunately, I don't have detailed wiring diagrams for either of them, so I can only offer general assistance.

For the ML95 Passat TDI, the glow plug wire from the instrument cluster pin 20 , via gn/ws, connects to the engine control unit pin 48 via a connector. The signal is connected to ground. When the lamp is on, you should measure approximately 0V against ground. When the lamp is off, you should measure approximately 12V on the wire.

At the end of the 96 AFN, it comes out of the control interface (KI) pin 13 via brown/green wire to the MSG pin 48.

The logic remains the same, but the pin configuration of the microcontroller has changed.

If you left the old AI (Artificial Intelligence) unit and wiring in place and only replaced the MSG (Message Service Module), it should actually work. So, the only thing to do is to check the continuity between MSG pin 48 and AI pin 20.

Regards,
Guste.

Hello!
Sorry for the late reply. I've been traveling a lot. Yes, first of all, thank you very much. I will definitely look into this. I will definitely let you know if it works.
Sure, here is the translation of the text from German to English:

"MFG" is an abbreviation for "Mit freundlichen Grüßen," which means "Sincerely" or "Best regards" in English.

Hello!
So, I've already measured that.
If I connect pin 20 of the instrument cluster to ground, the preheating light illuminates.
Then I connected pin 13 of the AI module to contact pin 20.
Then the LED will flash briefly only once.
Can someone tell me how to get the preheating LED to light up again during the preheating process?
It's actually an advantage in the winter to be able to see how long it takes for it to preheat.
If someone could help me with this, I would be very grateful.
Best regards, and thank you in advance.

"Hi, I had the same problem. There are two wires twisted together from pin 1 to pin 7 on the engine control unit connector, specifically the glow plug and heater control wires. Unfortunately, I don't remember the exact pin numbers anymore, but if you absolutely need them, I can figure it out. Also, I soldered a 1k resistor across the LED because the faint glow was still present."

Hello!
Okay, I've been driving with my fog lights on the whole time.
You get used to everything. So, if you know anything more specific about that,
I would be happy to resolve this issue.
Sure, here is the translation of the text from German to English:

"MFG" is an abbreviation for "Mit freundlichen Grüßen," which means "Sincerely" or "Best regards" in English.

Okay, I checked, and you need to swap pin 48 (blue/green) with pin 26 (black/brown) directly at the MSTG connector. One of those wires goes to the light bulb, and the other comes from the auxiliary heater relay on the splash guard. After that, the light bulb should work, but it will still glow dimly. Then, I added a 1 k ohm resistor in parallel with the light bulb (I soldered in an LED), and now it doesn't glow at all.

I cannot guarantee that this will be the case for you.

I converted my fuel injector from part number 1Z 028906021B to part number 028906021DF, which is compatible with a Golf 3 MSTG AFN engine.

Hello!
I tried it right away. And now the light is working.
Thank you for the tip. Regarding the 1kOhm resistor...
I will also do that. The child will have to do it anyway.
Reflow the solder joints due to the likely presence of dead solder joints.
Thank you again.

Good day, esteemed forum members,

I have a similar problem. But I don't have a solution yet, maybe you can help me.

Background:

The base vehicle is a Passat 35i B3, manufactured in 1992, with a 1.9 TD AAZ engine.

I recently had the opportunity to buy a donor car at a very good price. It's a Volkswagen Passat B4 1.9 TDI AFN, manufactured in 1996, with full equipment including electric seats, heated seats, cruise control, electric windows, climate control, central locking, and ABS.

This donor unit was missing the alternator, starter motor, and key.

Ich habe das Steuergerät weggebracht und die Wegfahrsperre deaktivieren lassen. The engine is running.

After that, I installed everything, including the central locking system and Climatronic, into the B3. It runs, drives, and brakes. I didn't install the airbag. I took it for a first, longer test drive, and during that, the electronic diesel MFA speedometer from Motometer almost melted.

I haven't found any obvious errors yet. I haven't tested the power windows and central locking system yet.

I've acquired another speedometer. However, this speedometer now exhibits the glow plug indicator light flickering, but it also shows the normal preheating indicator.

Have I forgotten to assemble something that could have caused the Tachobrand incident? I need your help to move forward.

Thank you very much.

Hello,

If the new instrument cluster doesn't have a traditional preheating lamp (incandescent bulb) but instead uses an orange LED, the problem might be that a minimal amount of current (a test current for incandescent filaments?) doesn't activate a traditional bulb at all, but it's enough to cause the LED to light up slightly.

To fix the issue, as mentioned above (I've corrected the value), add a 1 kOhm (1000 Ohm) resistor in parallel with the LED connection. Just check the wiring diagram to see how the wire from the ECU is connected, either to ground or to +12V.

The 0.25W power rating of the resistor should be sufficient. Everyone is happy because the control unit now sees a "glow plug test current," and the LED no longer flickers because the test current is flowing through the resistor instead of the LED.

Best regards, Rainer.

Hello Rainer,

Thank you for the quick response.

Do you have any idea why the speedometer was reading so high? Was it a fault in the speedometer itself, or was the problem caused by the ZE (likely referring to an electronic control unit)? The ZAS (likely referring to a sensor or module) is also new.

Passat35iAAZ wrote:

Hello Rainer, Thank you for the quick response. Do you have any idea why the speedometer was almost maxed out? Was it a fault in the speedometer itself, or did the error originate from the ZE (control unit)? The ZAS (sensor) is also new.

Incorrectly connected, or is the wiring slightly different?

That's exactly what my problem is.

"Does anyone have a wiring diagram for a 96 AFN for the instrument cluster, engine, and Climatronic with Econ? I'm not sure if the components are working correctly or if the wiring is wrong. The cruise control isn't working either, and the ABS is also showing an implausible error message. Also, relay 109 is getting very hot (I've already opened it, and it looks fine), and I can't access the MSG."