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?