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FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

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FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

Postby alfa164superwebmaster » Thu May 03, 2018 8:20 pm

Dear all,

As you could have read in my previous posts, I was struggling with the dreaded 'Error Piston Movement' problem after the rebuild of my Q4. Also with my previous Q4 i was facing this problem.

I tried to bleed the system with the Alfa Tester MA12A module numerous times, without success.
Als the Course Piston Parameter (piston movement) stayed at 0%, no matter what I tried.

So I decided to try to actuate the solenoid by hand, to see if the piston would move when controlled manually.
To do this, I purchased a PWM controller from Conrad.
The type I used was a Kemo Power Control M171 DC 5A

I connected the PWM controller to the solenoid on the viscomatic unit, and a 12V 2.5 A power supply from my wifi modem ;-)
When running the engine, I turned up the potentionmeter of the PWM controller.

After one or two full power settings, I hear a slight 'clunk' at the diff and I got 100% piston movement on the Alfa Tester!!
Disconnected the PWM controller and reconnected the Viscomatic ECU to the solenoid.

Everything now works like a dream.
So it seems the Viscomatic piston got stuck from standing still (car stood for 4 years).

The PWM controller is very handy for debugging the Viscomatic, so I hope this helps the Q4 drivers out there.
Pictures are attached.

Cheers!

pwm1.jpg
Viscomatic PWM controller 1


pwm2.jpg
Viscomatic PWM controller 2


pwm3.jpg
Viscomatic PWM controller 3
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Re: FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

Postby Alfan » Thu May 03, 2018 10:10 pm

Awesome!!!!!!!!!!

That is great work and thanks for sharing the info :D
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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Re: FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

Postby AlfaWhiz » Sat May 05, 2018 6:37 am

Great result! :D

Very glad to hear that you've fixed it, well thought out method. Good to have this trick on the sleeve as many of us had or still have this issue.
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Re: FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

Postby 164 TD » Sat May 05, 2018 11:46 am

Image

Still wondering what part of the gearbox the actual piston is. You can see the viscomatic coupling plates very clearly, but the piston that "squeezes" the viscomatic plates and the piston that actually mechanically connects the inputshaft to the viscomatic are hard to determine.
TD en Q4 owner

Image
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Re: FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

Postby AlfaWhiz » Mon Jul 09, 2018 10:58 pm

The piston is actually visible on the picture above, just left (or more towards the input shaft) of the Viscomatic coupling discs. It's drawn as a cutaway and you can see some of the void compartments where I believe the hydraulic fluid is actually acting on the piston.

visco_piston.JPG
visco_piston.JPG (23.28 KiB) Viewed 77 times


Here you can see it even better, its from the Steyr Puch or Magma Steyr documentation on Viscomatic:

visco_piston_steyr.JPG


Now after picking my car from the workshop where it sat for a while I seem to be facing the exact same problem. Error is bad piston movement and piston stays at 0%, Viscomatic is disengaging immediately after the throttle is pressed. I've tried to clear the code multiple times even when driving, counting that it would maybe warm up and start moving, but it looks that I'll be testing your new method with the PWM controller soon. :roll: :)

@alfa164superwebmaster can you post the details of how you connected the PWM to the actuator? Did you run an extra long wire from the cabin to the underside of the car or did you work from below the car? Which cables of the PWM module go where on which connector on the car? I know it's rather straightforward but would prefer not to make things worse...

Many thanks in advance! :)
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