Another no start - no crank low voltage

[TX82FIAT]

Every now and then i get a no start situation. The first gut reaction is the ignition switch. However, this last time i decided to toot the horn as an alway hot circuit for kicks when the no start situation presented itself. The horn gave off a very very low dying cow sound. I checked the bullet connection under the master cylinder by the alternator as well as the connection to the alternator and starter. All connections appear clean and tight. Ground straps and grounding pods are clean and in good shape all around the car. Car battery is fully charged per voltmeter.

Now the wierd part. Without fail, when the car has died and will not start with the low power issue. When i open the green nob on my battery and tighten it back down the car fires right up every time..... Why would disconnecting and reconnecting the battery cure a no start low voltage situation??? ideas, thoughts, help.

I almost ordered a new ignition switch.... but why then the horn no worky.

[azruss]

This is a connection issue. All connections need to be cleaned, not just the ground circuit. Sounds like your battery connection is the issue. You can get corrosion between the cable and the clamp. When you removed the clamp, you are moving it around just enough to rub stuff together to help the connection.

[majicwrench]

SO the car dies?? and then won't restart??

Connections, no need to clean "all the connections" there are hundreds of connections in your fiat. A simple test light once it is dead will find issue. Then you fix THE connection that is causing your problem.
I don't know anything about green knobs on batteries, but I would agree issue is likely right in that area and likely visable.
Keit

[aj81spider]

It's a Fiat, so the suggestions you got to check the connections are good ones. However the fact that disconnecting the battery resets it, if more than coincidence, would indicate there may be something else at work. When it is in the no-start state I would check the voltage at a couple of places: the battery, the starter, the fuze box.

When it happens are you just getting into a car that's been sitting, or trying to restart a car that's been running? Do you do anything besides turning the key?

I took a quick look at the schematics for the 82. There's nothing obvious that I could see that would reset, but taking a shot in the dark: do you have power windows and do you try to operate them before you start the car? The Power window relay looks like it's on the unswitched side, and if there was something drawing lots of current there it's possible it could be pulling the voltage down. If it's not a connection problem and it does get reset by disconnecting the battery that's the kind of thing I would be looking for - a stuck relay or a jammed motor that was drawing lots of current.

[TX82FIAT]

Good suggestions. I'll put the test light in the trunk so I can diagnose. I do have an amp in trunk with the circuit running off battery. Maybe the amp pulls power if radio on when starting car...