Boost Pressure Regulator N75 VW Golf III TDI 81kW

Hey guys,
'Papa's Golf' isn't running well. He says it feels like it's losing power on the highway, and also when accelerating. The lower RPM ranges seem normal.
That's why I read the error codes yesterday. The error code that came up was 575.
Intake manifold pressure - control difference - intermittent.
'Where can I find the magnetic valve for the boost pressure control (N75)? Can it be tested with 'standard' tools and measuring devices? I would really appreciate it if someone could help me.'
Best regards and thank you.
Bubu.

P.S. The car is a 1998 Volkswagen Golf Variant with an 81kW TDI engine. It has been converted to run on vegetable oil.

Hi,

You can only test the N75 electrically, meaning you can check if the coil has continuity. It has 3 hose connections and 2 wires (electrical), so it should be possible to locate it.
Unfortunately, it's difficult to determine if there are occasional mechanical issues. However, given the low price, I would simply recommend replacing it.

Best regards, Rainer.

Hello Rainer,
Thank you for your reply. I will try to find it now. Unfortunately, I couldn't find it yesterday. Then I'll check if it's electrically in good condition. Can I test it with a power supply (12 volts) to see if it's stuck?
Can Dad still drive about 300 km with it tomorrow? Or is something likely to break?

Thank you for your help.
Regards,
Bubu.

I found an interesting website today.
I think even someone with no prior knowledge can read this and understand how a TDI engine works.
http://...
[Link aus Urheberrechtsgründen rausgenommen. [Rainer]


Everyone should have seen it at least once .

Okay, so I was looking at the car, and I found a component where cables and hoses connect. One of the hoses goes to what looks like a pressure or vacuum sensor on the turbo. This component is bolted to the body near the right suspension spring. Is this the right part?
The measured resistance is 15.6 ohms.
If anyone knows where the valve is located, I would be very grateful if you could tell me.

Regards,
Bubu.


@Steffarn, thanks for the link. I'll take a look at it right away.

Wow, in Steffarn's link, you can see a drawing of the valve. But the valve we have looks different; it only has two hoses connected to it.
Regards,
Bubu.

Yes, unfortunately, this is a recording from a Wase-gate charger for a TDI engine.
Your Golf has a VTG turbocharger and valve. That only has 2 connections!

One hose comes from the VTG module, and the other is likely from the vacuum reservoir. During the actuator test, the valve is also activated.

I'll eat my hat if there aren't three instead of two hoses going to the valve. Make sure everything is perfectly aligned and trace the vacuum hose from the turbocharger back to its source.

How else is it supposed to work? *leaning out the window* Turning on your brain a little bit wouldn't hurt either. *leaning back and turning on the grill*

The only valve with two hoses that I know of is the one on the shut-off valve. It only has two positions: closed and open.

Steffarn wrote:

... In deinen Golf ist ja ein VTG Lader u. Valve.

Yes.

Steffarn wrote:

... It only has 2 connections. The one hose comes from the VTG module, and the other is probably from the vacuum reservoir. During the actuator test, the valve is also activated.

No. And then the valve opens just once to the "open" position, and the turbo stays in the maximum boost pressure setting forever, or what?

Oops, you're right, the vacuum needs a way to vent.
My mistake.

Below were 2 tubes (which were not visible), and on the side, there was 1 tube. The resistance was approximately 14.5 ohms.
'When I unplug the connector while the engine is running, I measure approximately 8 volts at the connector.'
The valve switches on the power supply, but the airflow is extremely restricted.
Soll ich das jetzt einfach tauschen oder lieber nicht?? Is it broken?

Thank you for your answers.

Regards,
Bubu.

Hi,

"Please look for an article by Ulf that explains the function of this valve. He analyzed a similar component and discovered that it's not simply an on/off switch. Instead, it works by having an iron core that oscillates up and down due to the pulsed voltage (around 8 volts!), and it mixes ambient air with vacuum in a way similar to a mixing valve in a sanitary setting. This creates a controllable vacuum that is then applied to the pressure sensor."

Simply applying voltage probably wouldn't achieve much.

Best regards,

Jan.

Hmmm, something about this thing is really weird. I'm not sure if I should replace it. On the other hand, I know that everything is sealed down there and the hoses fit. The wiring also seems correct because there's voltage at the connector when the engine is running. And the error memory keeps throwing up that annoying error...
Should I get this thing replaced? Does the reported issue match my symptoms? The car struggles to go uphill (we have quite a few hills here in Bavaria), sometimes not even reaching 60 km/h, and you have to force it up in 2nd or 3rd gear. Before, you could drive up at 100 km/h in 5th gear. On the highway, it's useless at 120 km/h, and it pulls less than my mom's ancient 90-horsepower Espace.
Is it likely that this stupid thing is going to break down?

Thank you for your help.

Bubu.

What else do you want to hear?

Rainer K. wrote:

What else do you actually want to hear?

"Wie wäre es mit:" kann übersetzt werden als:

* "How about..."
* "What about..."
* "How about we..."
* "What do you say to..."
* "Fancy..." (informal, British English)
* "What if..."
"Implement LDA to be able to see the error in real-time."
"Log the target and actual boost pressure."

What is the purpose of having such options available?
"Those who are hesitant about such an investment often end up buying a TDI engine blindly, without knowing much about it."

Since the part only costs about 30 euros, the decision shouldn't be too difficult. I also replaced the solenoid valve in my car. The dealership had 8 in stock. That's already enough of an indication that the part is prone to failure. However, a proper diagnosis of the measured values is definitely helpful.

Best regards, Holger.