trouble with pacelite hcf 707

Hi all,
I have a problem with my step.
Normaly I turn the key and there are 3 lights and I can drive away.
Now there are 2 lights and it takes about 1-2 minutes before the 3 light goes on
The step does nothing before the 3 light burns but after it lights up the step works.
Does anyone know whta the problem could be, my batteries are 2 years old

Thanks for your help and time
Gerard