So the ignition light is constantly on but the alternator is charging the battery . Battery voltage engine off 12.6v engine running 14.8v. Ford 302 single wire alternator Proform 100. Voltage on red cable to lamp engine off 12.6v running 14.8v. Other cable to lamp (blue) goes to earth both with engine off and on. Explains why ignition light is constantly on. Question:is there anything else I can do or as I suspect take the alternator off to be tested for a low voltage return. Must admit I don't really understand how single cable alternators work. Any help appreciated. My local auto electrician says a single terminal alternator can’t support an ignition warning light and must be another warning light such as
oil pressure but it hasn’t got an
oil pressure light just a pressure gauge. Thing is it used to go out with the engine running then became intermittently on before being permanently on.
Dek