"Chris" wrote in message
...
Before I take a look inside (or bin the thing) I just
wondered if anyone had an idea what might have gone kaput.


I guess you old charger contains nothing more than a big transformer
and a bridge rectifier. The rectifier contains 4 diodes to convert the
AC from the transformer to the DC for the battery. If one of the
diodes goes short circuit then you will get the effect you are seeing.

If you really want to resurrect the charger you could probably replace
the old bridge rectifier with a new one from Maplins for couple of
quid (AR84F looks suitable). But as modern cars and batteries are more
susceptible to mistreatment I would be tempted to just get rid of it.

Thanks for the quick replies. I have now taken the back off and yes it
does look very basic inside. I can see the rectifier which has 4
connectors and a hole in the middle screwed into a thin sheet of metal
(or is that a heatshield). It has writing on the rectifier which says;

S4VB
10 (Hole) 84

I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
looked at the Maplin code for AR84F and that is 25A. Would it cause any
problems using a higher amp or is it best to keep with a 10A? Cheers.