I find them very variable sometimes not visible at all
I would not get too overly concerned if the thing does not appear to work

 

Agreed,if the indicator shows black,usually the car will unable to start.

 

Even when my car was new, i was unable to tell if it looked dark green or black. Still looks just the same after 5yrs.

 

I don't know how the indicator works, but when it's working properly and the battery's in a normal charged state, the colour seen is a bright fluorescent green. There's no mistaking it. If anyone knows how the 'light' works maybe we could figure what happens when it changes.

TC

 

green light

Hi Its not a light its a ball in a tube its a hydrometer as the s/g of the battery acid changes the ball is higher in the tube so it is brighter as it sinks acid over the ball is deeper so not as bright at the base you cant see it at all

 

Ah, thanks andrewmsteve. So it should be more or less foolproof. Can't see how a floating plastic ball can do any other than float or sink according the the density of the acid. I suppose it could get coated in detritus and loose its fluorescent green appearance.

TC

 

Grand job so, cheers for that Andrewmsteve.

 

I wouldn't worry about it - since I got my car 10 months ago the battery indicators says it has a problem and the car has always started fine. Seems like these indicators were a good idea poorly executed.

 

Yes mine is black but still works fine, might think about replacing before the winter though - just to be sure!!
mrbukie