Drove my car home after having the new Gearbox fitted (thanks Bernie and SCC ) and noticed some very strange things things happen when i turned my heater on/off.

I've just fitted a new cossie pump which has a louder buzz compared to the std RST one (which is probably why i've only just noticed the problem), but when i turned my heater on and off the buzz tone would drop for fraction of a second. I also noticed this when it started from cold later that day, every time the car hunted and revs dropped the buzz from the pump also changed note.

So volt meter out.....

Volts from Altornator @ idle 14.13 (holds this value when engine revs increase)
Volts from Batt @ Idle 14.1 (holds this value when engine revs increase)
But when i turn my heater on it drops to around 13.7 @ the alternator.

I then checked the fuel pump, 14v @ idle but when i flick the heater on and off it dropped again to 13.7 and the pump buzzing sound dropped and picked up again.

I've checked all earths and as much wiring as possible and seems all ok. Does this sound like a dodgy alternator regulator? I've recently fitted a new reconditioned alternator could this be faulty?

Cheers,
Dan