All Things Chev

[MB]

.....the alternator was charging at circa 14.2- 14.3 when first put in, now 13.8 seems the limit.

That and worse was exactly what I experienced Phil. In fairness the Mitsubishi alternator on mine was in for a few years with me and unsure of for how long before.
Very happy so far with your kindly advised GQ 170amp Ebay weapon. I foolishly drained my Aux Optima down to 10.5V with an electric blanket in the mountains recently and without proper documented tests seemed to be back up within an hour or two after departure next morning.