Speedo/rev counter not workin

[Castrothecat]

Hi folks,
Is there anyone who can assist with this fault? We have a 1995 1.3GL and we are about to pass it to our son as his first car, however it has a few quirks, firstly the speedo and revcounter rarely work, most often the rev counter will vibrate about 1mm up and down and the speedo is stationary. I have taken out the speed sensor on the gearbox, cleaned it, the connections and the plug and it came back to life after starting then once the ignition was off and it was restarted we were back to square one
... next I was going to buy a new sensor.....