Intermittent Start up issues MK4

Symptom: upon turning ignition switch to ACC. just before cranking engine. the dash lights all go off and the trip and clock display reset. Everything goes blank and dome light dims. At other times all indicators are normal for start up (waiting for the glow plugs ok signal) and at start up request nothing happens.
Secondary Symptom; ignition key in ACC. clutch depressed- all lights and sound along with doors auto lock begin to blink, clank,and sound. If I request start up it symptoms don't change.
What I have done so far:
1.Replaced ignition switch (4B0-905-849) because when I wiggle the key the car would start. It was good for 1 day and symptoms returned. Replaced the old one and continued to drive the car with a flat head screwdriver directly to the switch. Yesterday the car stopped responding, even when I swapped old and new ignition switch.
2. I reseated the fuses in the flat black container that comes off the positive (red) cable of the battery. I was told that poor connection here could be a cause.
3. Push start the car and then it works, until it doesn't
4: Battery is brand new; purchased in October of 2017.
5. Took it to a mechanic and they could not find any problems; because the freaking car was working fine!
Please help out if you have seen this issue before.

Did you check the grounds under the battery? This sounds like you have an intermittent high-resistance connection, and the most-likely place for it that impacts EVERYTHING at once is in the ground side.

"Brand new battery" doesn't rule out that the battery's bad. Verify that the battery is in fact good. It could have been teetering on the edge when you got it (low end of the manufacturing QA curve) and a cell had died. Might be it's gotten overcharged (and damaged/killed a cell).

Do voltage drop tests. Is power really being drawn at all?

Thanks>
I will recheck the Batt and Vdrop. and reinspect the grounds under the Batt.

Also check the battery cables are clean and tight on the battery. When the lights go out that would be the time to do the voltage drop tests.

wonneber said:

Also check the battery cables are clean and tight on the battery. When the lights go out that would be the time to do the voltage drop tests.

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^ This but also make sure that both ends of both battery cables are removed, cleaned with a wire brush and reinstalled tight.

Thank you to the Veteran members! Problems solved.
The 4 ground terminals under the battery were coated with a brownish paste like substance. I cleaned and applied dielectric grease for better contact and the problem is no long a issue.

dzljedi said:

Thank you to the Veteran members! Problems solved.
The 4 ground terminals under the battery were coated with a brownish paste like substance. I cleaned and applied dielectric grease for better contact and the problem is no long a issue.

Click to expand...

Great you found the problem.
Thanks for posting the solution.