Mk1 battery issue?

[Patch888]

Hi guys, my battery light on the dash seems to flash at will, never stays on and on some journeys it doesn't come on at all. Seems to be after about 10 minutes into the drive and more so under spirited driving. It doesn't seem to stay on longer than a second, I can't put my finger on it. Also the battery is a non gel type, is it worth changing ASAP or charging? It's on a 1991 1.6 uk car, thanks for any help.

[ronime]

That's not the battery light it is the alternator light. It means that your alternator is not generating enough voltage or you have a bad connection to your alternator.

[Patch888]

Cheers, how do I diagnose the problem? It's sometimes on when I first start the car. New alternator?

[spoodler]

Always start with the cheapest fix. Check that the alternator drive belt is properly adjusted before any further panic.

[Patch888]

How do I check its correctly adjusted? It seems to have a few mm give in it but pretty solid.

[ronime]

The alternator has two electrical connections. An eyelet terminal for the earth side and a plug connector for the 12V positive side.

Check that the terminals/connectors are securely in place and that the contacts are not corroded.

[Patch888]

Will check that, thanks.

[Patch888]

Well that all seems in order guys, popping it in the local mx5 garage tommowow.

[renaultgeek]

check that the terminals are connected without any corrosion or crust and that they're tight, mine went to pot and for a while before I replaced them I had to wedge a self tapping screw between the terminal and the battery.

[NiceCupOfTea]

Yes, especially with a wet battery. Probably won't be fixed down properly so will be movement and probably a weakened earth strap... Check before it snaps. Or could well be the alternator regulator/brushes - at a few quid much cheaper and quicker than replacing the alternator.

[Patch888]

Cheers guys, the garage is looking at the motor tommowow, been there since yesterday. Battery is tightly strapped in the back, no movement etc. Alternator light only appeared to flicker when over 3.5k or 60 ish mph.

[ronime]

Patch888 said:

Cheers guys, the garage is looking at the motor tommowow, been there since yesterday. Battery is tightly strapped in the back, no movement etc. Alternator light only appeared to flicker when over 3.5k or 60 ish mph.

Possibly carbon brushes in the alternator on their way out (floating over the commutator).

[Patch888]

The belt was very loose and has now been tightened, hopefully this will have sorted the problem as it appears at random.