1. All earth leads checked and are OK
2. Alternator removed and tested by auto electrican - no problems at all
3. New battery purchased from Fiat main dealer - still same problem
4. Voltmeter shows 13.5V when engine running
5. When battery does not turn over the starter, the lights still seem bright and the blower and wipers work fine without slowing down.
6. We have removed fuses for radio and interior lights in case of a drain on the battery
7. We have noticed that when vehicle doesn't turn over, turning the headlights on will sometimes spark it into life!

Andoo said:

Has the sparky checked that the alternator is producing amps?

It's all very well producing 13.2v, but it needs to produce around 60/70 amps on a small engine like that.

I think the alternator needs further checking. We had a similar fault in an alternator on a Rover two weeks ago. It was fine for a day or two then the battery would go flat.

The ignition warning lamp and load sensor wires had been bodged by a clown who wired them back to front.

However, this was a red herring. The alternator was gubbed. New alternator fitted, job done.

Turned out the heat shield was missing from the exhaust manifold so over time, the plastics on the alternator had become brittle and warped, allowing all manner of twisting of metal wires and components on the voltage rectifier.

When the car sat for a while, the heat build up under the bonnet was enough for a short to occur, which drained the battery very quickly as it was never getting a serious charge. Driving along in the dark with lights, radio & heater just killed it.

Get an alternator load test done. Halfords do them free if I recall

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