Battery light issues?

I have a 2010 ford bantam 1.3 rocam petrol, I drove to work one morning
with all
normal. The afternoon when i started, the battery light did not go off, I limped
home and measured the output voltage of the alternator with a digital multi-
meter
set to dc at idle of below 1000rpm that the voltage fluctuated from 2v al the
way
to 22v. When the engine is idling above 2000rpm the light will flash erratically
on
and off and eventually didn't come on any more. i also stopped the excessive
revving since this wasn't helping at all. I inspected the alternator, no burnt
wires,
no funny smells,so i changed the alternator regulator. After the new regulator
was
installed al worked as advertised. Went for the test drive and on the way out
of
the yard , waiting for the gate to open at idle the battery came back on again.
Turned around and went to test the output voltage again. The brand new
alternator regulator is also giving fluctuation voltages with the dmm set to dc
below 1000rpm. When the engine is idled above 1000rpm the battery
indicator
goes out on the dashboard. Havent drove around as yet, i dont know if the
erratic
voltage fluctuation might have damaged the battery or the instrument cluster.
The
battery is about 18 months old, so its relatively new. I also live in a hot
environment, so chances that the battery got cold shock in the winter is
virtually
zero. What is my options from here on further,? Thanks for any advice in
advance