Technical Ignition light on unless I rev the engine

[ClassicFiat500]

Just re started Little Ava after a few months of being laid up after a carb rebuild & house move. I used a battery boost which I have used before as the battery was low, however when it started I didn’t disconnect it immediately as I should. Now the ignition light is glowing, it dims when I increase the revs. The engine is a 652cc with an alternator & electronic ignition. Is it possible I have screwed up the alternator? All advise would be welcome. Go on I can take it!:bang::bang::bang::bang::bang::bang:
Barry

 

[JumpJet]

Get a multi-meter on it before your worry too much. See what the alternator is putting out at different revs. If it's something as simple as the voltage regulator, it's a relatively inexpensive and easy fix.

 

[ClassicFiat500]

Hi Matt sorry to sound thick, I have a multi meter where should I test on Little Ava ?

 

[JumpJet]

Apologies. Ensure it's set to DC mode and the scale that supports 14 volts (usually there's a 20V range). With the car off, put the red lead on the battery positive post and the black on a good ground. That should read ~12v, indicating a charged battery.

Have a helper crank/try to start the engine and see where the voltage drops to. It shouldn't go to zero. If it does, it won't crank, but that's a sign of a bad battery and, since it's starting for you, shouldn't be an issue.

So, start 'er up and let it idle. See what the output voltage is - it should be ~11-13 volts at idle. Rev it up a little, nothing crazy, if you have a tach, 1500-2000 is more than sufficient, and see what the voltage reads. If it's not a steady 14V, you've got an alternator problem.

That's the quick way to test it. There's a specific way to test the voltage regulator, but let me search around for that process (unless someone chimes in first).

 

[ClassicFiat500]

Thanks Matt, will give it a go later this week, I hope its not the alternator as it looks a nightmare to remove
Barry

 

[fiat500]

Now the ignition light is glowing, it dims when I increase the revs.

It is most likely to be a bad connection in the low tension circuit which goes via the ignition switch, the IWL and the smallest gauge spaded wire at the alternator. It might even be temporarily sorted by wiggling connections.

 

[ClassicFiat500]

Hi Fiat 500 Hope you are right , as Matt said I will test it with a multi meter but 1st check all the connections. The last thing I want is to change the alternator.
Barry