Battery Light wont go off

[Deeman]

Chaps - I have read a few other threads on this but wanted to check with the S owners before attacking with multimeter and going on a wild goose chase. Context is, since coming back off holiday, battery went flat (I stupidly didn't trickle) - replaced battery, then dislodged crusty earth and causes problems. Now new battery, earthings fine and go for a drive last night, switch off and battery light comes on. Being late at night, thought i'd leave on trickle and check in morning. Light still on and alternator still hot! I was going to check charging from alternator, but the batt light didn't go on whilst running and still doesn't. Its just when you turn off and take out keys. Now of course worried its going to drain the new battery!. Any advice welcomed.

[Oldred_V8S]

Deeman said:

Chaps - I have read a few other threads on this but wanted to check with the S owners before attacking with multimeter and going on a wild goose chase. Context is, since coming back off holiday, battery went flat (I stupidly didn't trickle) - replaced battery, then dislodged crusty earth and causes problems. Now new battery, earthings fine and go for a drive last night, switch off and battery light comes on. Being late at night, thought i'd leave on trickle and check in morning. Light still on and alternator still hot! I was going to check charging from alternator, but the batt light didn't go on whilst running and still doesn't. Its just when you turn off and take out keys. Now of course worried its going to drain the new battery!. Any advice welcomed.

Sounds like the alternator rectifier. Not difficult to repair and certainly a lot cheaper than a replacement alternator. I got a repair kit for mine (for my spares kit) for about £20.

[Deeman]

Paul thanks for the advice - will look into it. Definitely something's amiss. Checked Battery and 12.5v registered no alternator running. Alternator running is picks up to 13.1 13.2. The run last night, was way over 3000 rpm, so would have been charging. Pete

[Deeman]

This saga continued - made sure I had all earth's sound, and new earthing straps, new battery etc. Then battery light when on whilst driving (and over charge revs of 3000). Then went off after more fiddling, and replaced by a pulsing battery light on dash whilst driving - still reckoned the alternator was giving charge at 12.5 static and 13.2 engine running. Found a non exchange alternator (£80), modified a few of the connections to it and bunged it in today and hey presto, all problems have finally gone!! (and it all started by not trickle charging whilst on holiday for two weeks - joy!) At least I now know its all new and shouldn't give any more problems for a while.