Is it the alternator, or is it the battery?

[louis]

This is my first post - forgive me for diving straight it but I'm a little short of time. Promise I'll introduce myself later!

The red charging light - or "battery" light - is on at low revs. Measuring the input across the battery terminals with a multi-meter shows just over 14 volts. This looks about right to me, so am I right in assuming I need a new battery?

Thanks for any advice! (And hello Clementine!)

 

[malcolm]

Welcome to the forum. Clementine says hi too.

What year is your car? a red light at idle would mean the car is using more electricity than the alternator is producing. R4s made before about 1975 had dynamos, and that would be typical for a dynamo, especially if it's a bit worn. (Dynamos look like long smooth steel cylinders where alternators are shorter and have mostly aluminium casings.)

If it's a normal alternator car then my guess would be a fault with the alternator, or a current drain (unlikely because 14V is about right for the battery), or bad connections to the alternator, or a bad earth on the thick wire that screws to the front of the right side inner wing.

 

[angel]

From your description (red charging light...) I suppose your car has an alternator. Dynamo equipped cars had green charge lights!

Don't confuse the "charge" lamp with battery condition, it has no relationship whatsoever.
Since you getcharging voltage at the battery, I cannot think anything else except a faulty voltage regulator. Check also all connections as Malcolm suggested.

 

[louis]

Connections - of course!

My tenuous knowledge of electrical gubbins makes me think it's unlikely to be the regulator. Surely, if this were the case, the light would be on at all revs?

The car is an '84, made in Espana. I've owned it for about five years. I don't think there's a straight panel on the thing - but it was like that when I got it. Honest!