Another update, owners been driving the car as is which has been just fine. Only working on it briefly over weekends and some evenings as we are both quite busy and live a good hour and a half apart.

Unit still wasn't working correctly, no flow registering so after contacting Aquamist it was determined something was stuck inside the flow meter. I took it out and got it to register flow while blowing air through to spin the turbine. But it only works for a short period and then stops again.

I just received detailed instructions on disassembling the flow meter and checking clearances and cleaning. I'll post the pictures of the operation tomorrow when I've completed the stripdown.

Annoying but light is appearing at the end of this tunnel...