I hadn't had any problem at all, until suddenly the car was completely DEAD. Zero power. The battery connections are clean and tight, but a wiggle of the positive cable brings back everything, until I try to start the car, and then there's a click-like sound (Relais?) and everything is dead again.

What could this be other than the connection at the battery posts, which seem to be as good as possible and I've never had this problem before?

Thanks for your time and input!

M.i.M.

That sure sounds like a cable/posts/connectors problem Mike, but it could be the post internal to the battery, as I had that happen with a cracked plate/post connection inside a relatively new battery once years ago on my 325e E30. If it's the battery & still under warranty, then they should replace it for you.

The cable could've split somewhere too, usually close to the connectors or at a tight bend, that gets some connection when wiggled.

Good Luck!
Tom
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Sounds like a bad crimp on the cable. I had this happen to me too.

The ground cable looked fine but the crimp had failed and the cable was barely making contact with the clamp.
I could easily pull the two apart by hand ...

What about the other group of red wire off of the positive terminal ? I would check for corrosion or bad crimps.

Is there a ground strap on the trans to body?
Positive wire connections at starter?

This happened to me too with my old 1.7. I was chasing my tail trying to figure out why the car was seemingly slower than the Ghia I owned at the time. I went through everything I could think of.
There would be rare moments where the car would have full power, but mostly it didn't.
Finally I was trying to fix some unrelated electrical issue and I undid the negative battery terminal and the connector simply broke off from the ground cable. Replacing the battery terminal connector completely solved the issue.
It seemed that at times there was enough contact being made by the broken connection to give full power, and other times there wasn't.

Does the pos cable have integral clamp?

It is possible that you have oxidation between the clamp and the pos terminal. When it dies, measure the voltage from the pos terminal on the battery to chassis ground. Then measure the voltage from the pos clamp to ground. They should be the same.

I had the same thing happen. Good start; good start; dead; good start... Took off the pos and neg clamps, cleaned and reinstalled. Never had another issue: same battery; same cables.

I agree with Andy. Bad cable crimp

My starter was just replaced last week. Before that I had no problem at all. Guess I should have mentioned that? Will have to check. The grounds should be fine.

M.