Alternator only putting out 12.3 v after Tachgraph fitted ?

[Karl1967]

As the Title, After the tachgraph was fitted it throw up a power interuption warning on the tacho and has done a few times since , The alternator is only showing 12.3 v when testing on the running vehicle , Lights dipping when clutch pressed on dash and exterior headlights etc for a second or 2.

Alternator just removed and tested and is putting out 14v and is absolutely fine. What could be causing this from just having a tachograph fitted. Vehicle is a isuzu Dmax , Any help or advice much appreciated.

 

[PEG]

Hi,bit late to reply,but will have a go...
Is the charge warning light/function working?

Has the vehicle charging system been tested in real time,with a suitable analyser,as it may well be some development of smart-charge technology.

The tacho will maybe have a running live,as well as a permanent live,and if this is taken from the wrong part of the alternator circuit,it will upset the PWM signal,which controls charge output.