In message , Gib Bogle
writes
On 5/06/2012 9:52 p.m., Dave Plowman (News) wrote:
In ,
Gib wrote:
While testing things I noticed my battery voltage was very high (I'd
just been running the engine). With the engine running the charging
voltage is about 19v. A new, probably more serious, problem. It's a
bit of a coincidence, so I'm wondering if they are linked. Could the
high battery voltage have caused the motor to fail? I'm familiar with
low or no voltage from the alternator, but I don't know what can cause a
high voltage.

Assuming your DVM hasn't failed - it is reading some 12.5v from the
battery with the engine stopped? - the alternator regulator has failed.
This is usually internal to the alternator but can be replaced for about
£30 if you can be bothered finding one.

Unless the rear wiper was in use for a long period, it's unlikely this
high voltage will have caused it to fail.


There are a couple of things going on here that I don't understand.
After sitting overnight the battery still reads 18v, engine not
started. This shows on three different scales of the DVM. Not
believing it, I checked with my old analog meter - same thing. How can
a 12v battery hold 18v of charge?
When it's been seriously overcharged. Normally it is charged at 13.8v
and when the engine is switched off it will decrease down to 12v. To
stay at 18v overnight is a bit unusual though IMO.
--
hugh