Post
by KevR » Thu Jun 09, 2016 11:03 am
I had the same problem - turned out to be a worn slip ring on the alternator. As a test, try running the engine and putting a volt meter across the battery. Assuming it's not charging (battery probably at 12-13v), then get suitable long bit of wood, apply to the body of the alternator, and give it a couple of sharp taps with a mallet. This can quite often allow the alternator brushes to dislodge a bit and make contact again, in which case you'll suddenly find you'll have charging voltage (around 14v) at the battery. Drove one of mine around for months like this giving it a tap every few days before I finally got round to replacing it!
New slip rings and bushes are cheap enough, but you will need some soldering skills.
<edit> Note to self - read the original post properly. As has been said above, the fact the red light's on with ignition off probably means it's a diode rather than the slip rings. Still worth hitting it a bit though - might not do anything useful, but you'll feel better....
1990 BX TZD Estate ('the grey one', 1991 BX TZD Estate ('the white one'), 1982 2CV6 Charleston (in bits), 1972 AZU Serie B (2CV van), 1974 HY72 Camper, 1990 Land Rover 110 diesel LWB, 1957 Mobylette AV76, 1992 Ducati 400SS, 1966 VW Beetle, 1990 Mazda MX-5, 1996 Peugeot 106D, 1974 JCB 2D MkII, 1997 BMW R1100RS, 1987 Suzuki GSX-R1100, 1978 Honda CX500A, 1965 Motobecane Cady, 1988 Honda Bros/Africa Twin, 1963 Massey Ferguson 825, and a lot of bicycles!