ignition light stays on - but

[shropshire lad]

Started the car (chimaera 500 serpentine) this morning and the ignition light stays on , well glows at least.I assumed loose belt or alternator gone. Belt seems really tight and is turning the alternator pulley, therefore must be alternator .
However when I took the revs up to 300rpm light goes out. Whats all that about then ? I thought alternators either worked or they don't. Could it be the thing is on its way out or is there another remedy ?

[Vee8]

I'm not sure if this is of any use, but I had a similar problem with my Spitfire some 25 years ago. Gawd. It transpired to be a short within the alternator. If left would drain the battery.

Best get it sorted by an auto electrician

[shropshire lad]

I tend to agree. Thanks

[cloggy]

Could be the 100 amp fuse, see thread below.

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[chelseawiggie11]

i agree....my light was glowing faintly.....changed 100amp fuse and all was fine.....