Spitfire 1500 electronic rev counter reading 7000 rpm

[Colin Lindsay]

I've recently sold one of these online and the buyer tells me that every time he connects it up (a 1977 Dolomite 1300 with standard ignition) it registers 7000 rpm and stays there without moving.

I've sent him the wiring diagram and he says this is the way he has set it up, and the car has standard ignition but he is soon to change to electronic. As far as I know - and the photos I took of it don't tell me - it's an RVC unit and not an RVI.

Anyone have any ideas of what the problem might be?