Bri,
since you've mentioned that you're au fait with sensors, have you managed to find a commercially available replacement for the original Visa proximity sensors?

After about 10 years of running our 2 pot Visa, I've now got a collection of black boxes, at least 3 of which are no longer functional.
2 of those were made by Motorola, the other came from Thompson-Brandt.
After having a look at the circuit boards, all I can deduce is that none of them are the same.
One has 2 power transistors, the second unit is superficially similar to the first, but has a blank heat sink where the second transistor would have been located.
The third unit (8 contact type) has a completely different layout.

Anyway, back to your question about Visa black boxes...
I think that Mike Phelan, over on 2CVGB's forum, may well have investigated the workings of these devices in some depth.
He did send me a copy of some notes he'd made, but I wasn't able to make much headway with them.

ken

not looked at sensors yet but will be looking at sourcing replacements ASAP.
we arn't sure if we are having trouble with black box's or with coils.
might need the contact details for Mike if you have them you can PM them or i can send a email address.

Brian

Here are the schematics
F= wire
GR=Grey
VE=green
m=ground -
J=yellow

BC=white
MR=brown
BL=blue
R=red

I just checked it out, a sensor has 0.5 to 2 volt and when the magnet passes
it must have 5 to 7 volt.

At idle ignition happens when the magnet passes the first sensor at 10 degrees,
when rpm increases then the computer calculates a point between the first and the second sensor relative to the rpm (senso nr.2 is at 35 degrees).

When the pressure box kicks in (at cruising speed) ignition advances 10 degrees extra to safe fuel.

The wire to the coil can be tested also... when you turn ignition the wire (nr 8) to the coil has to have current for a short moment and then return to zero.

I'm sorry but I haven't opend an ecu yet.

1 ecu from me has gone because of the wire nr 8 has come loose at the coil
making contact for some moments and then not, I drove 5 miles like that thougt that a sensor was gone but it was the nr 8 wire..... then my ECu died.

I always carry a second ecu and at least 1 sensor with me in visa engined cars.
and ofcours a 21mm tool.


Take a look if the sensors are at the right distants of the sensor it should be around 0.5 to 1mm. When it is to close it starts to wissle when it is even closer
it will rip the sensor in pieces........ When it is to far away you don't have ignition.......

Hope I could help you.