Old Carver Motor Mover How do I reset it??

Hi I have an old carver caravan mover which worked intermitently,The printed board has just one reset button,with only one Yellow LED.When I press the reset button it flashes for a few seconds which I know to be correct,after this it should show the LED on and stable,but it is not staying on just goes off so I cant setup the handset to the panel any ideas Thanks Dinger.