Thanks buggy#0 and fletcher.
I changed the motor sensor wire. Worked find for a bit then started cutting out again.
I believe the thermal cut off is off but will reset everthing to see if that works.
The motor sonsor wire that came with the speedo is very loose fitting. Got one with a TrackStar motor which fits better.
The cars been running fantastically but all of a sudden this has cropped up. Will try rewiring the motor up again to see how that works.
The troubles of buying second had cars and electronis - sometimes issues crop up
