seamus wrote:
I am an electrician in Ireland, and came across a problem a few days
ago.
I was investigating why a motor of a washing machine in a commercial
laundry would not spin correctly and found the cables going from the
tacho generator to the control electronic were causing the problem, I
rerouted the cables and found all worked ok.

I suspect some form of mutual inductance, the tacho cables only carry
a small voltage, but was in a loom with many main voltage cables, Did
anyone ever come across a similar problem ? If so what is the best way
of identifying the problem, would an oscilloscope be required. Even
though I know I sorted out the problem I would like to know the best
way of testing for this problem .

Sounds to me like your experience, which made you suspicious of lead
dress as a possibility, was the best troubleshooting tool for that job.
A 'scope might have shown you noise on the tach wires, but might not
have helped you determine its source.

--
All relevant people are pertinent.
All rude people are impertinent.
Therefore, no rude people are relevant.
-- Solomon W. Golomb