Check your battery Ground to chassis. If the connection is good, do a voltage drop test on the ground cable

Number 3,4 and 5.

Hi,

I had a similar thing with my car, clicks but no electric windows and the even central locks wouldn't work - All I needed was a new battery (but that might be not your case)

Ideally, the best test would be installing with a known good battery and seeing how it affects the car.

But you can try testing if all fuses (that should be live, major components like the ECU - and please avoid swapping them around...) in all fuseboxes are live on both sides, and work from there.

Personally I think it's either a bad battery (caused by a bad alternator / lack of quality / ...) or a blown fuse... anything else (like an ECU) could get very expensive...

But generally these Italian cars have a reputation for crappy electronics, and you might end up needing to see an electrician.

(Also this is a 10 year old FIAT with over 100k miles on the road - I would not recommend spending any real money on it if it...)

1. This might be the reason.

2. That wouldn't explain no dash lights

3. Possibly but I doubt it, test things like map lights or other things that don't depend on that switch (I'm unsure what that would be on a FIAT)

4. This is highly probable

5. Apparently Fiats have those on the battery terminals so it's worth checking...

6 + 7. that wouldn't explain it failing to jumpstart

8 + 9. As I see it that wouldn't explain why there's no dash lights...

Your test probe is providing a path to ground. Check battery ground connections and cables and the ground cable between the engine block and chassis.

I have a 2012 Fiat 500. I posted my problem previously on: https://carkiller.com/scottykilmer/qa/2012-fiat-500-no-electricity-at-all/

Basically, my car's electrical system does not work at all. 

I checked the battery with a load tester, says it's a good battery with 12.89 V. I checked all fuses - not one got blown. The ignition switch, checked with the power probe, looks good.

A strange thing happened when I was checking the indoor fusebox with my power probe.

I put one end to the battery + side, one end to the battery - side, and as I put one other ground end to the chassis - I saw a spark and the car suddenly gets power back - though it does not crank. When I cut the connection, the power goes off. What the hell is going on here? I literally have no idea. I'm guessing I should see an electrician for this dumb car, but I just wanna get a little hint.

Video:

https://www.youtube.com/shorts/_RQBRx0oIh0?&ab_channel=steveioe

The battery could go bad internally