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FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

PostPosted: Thu May 03, 2018 8:20 pm
by alfa164superwebmaster
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

Re: FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

PostPosted: Thu May 03, 2018 10:10 pm
by Alfan
Awesome!!!!!!!!!!

That is great work and thanks for sharing the info :D

Re: FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

PostPosted: Sat May 05, 2018 6:37 am
by AlfaWhiz
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.

Re: FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

PostPosted: Sat May 05, 2018 11:46 am
by 164 TD
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.