Rover 25 - My battery light starts flickering on/off on the dashboard

Question

My girlfriend noticed this yesterday and thought it was odd, it stopped but started happening again this morning on my way to work, I think its a V plate.... "as I’m driving along my battery light starts flickering on/off on the dashboard. Have googled it and seen on some MG/Rover forum that it may be a dodgy alternator. or the battery on its way out."

I know the alternator can stick, not sure how to solve this any ideas guys?

She said she was going to get her battery checked by the battery guys near here work which isn't a bad idea as long as they don't feed in lies and say it does when it doesn't need replacing

Answer 1

There are three common causes for this issue. Two of them are the ones you have identified (failing batery or alternator), the third is the simplest - a poor connection or broken wire from the alternator. This latter you should be able to check with a multimeter, There should be a small wire coming from the back of the alternator to the dashboard carrying the charge signal (your workshop manual should tell you which one if it isn't obvious).

Unfortunately, both batteries and alternators have fairly short lives, and given the quoted age of the car I would expect both to be near to needing replacement (V is 2000, so 11 years old) if they have not been done already - alternators typically last 8-10 years and batteries less than that.

Answer 2

A loose/slipping belt could also cause the light to flicker.

Answer 3

If you notice that the flickering varies by engine speed or occurs only within a specific RPM range, I would bump the alternator higher on the list of possibilities. The light is usually off when the alternator is working, i.e. more voltage coming out than is applied at the rotor (spinny electromagnet inside).

A cheap fix could be to replace the brushes in the alternator. Sometimes a connection comes loose on the rotor itself, making a replacement of the whole thing a better idea.