My outside sensor light stays on dim is that normal?

Why does my sensor light outside stay on dim do all lambs do this now as all my old ones never did

Check the sensor. Some motion detectors have a setting such that the light are on dim for a specified period after dark and switch to full brightness when motion is detected.

I have some lights similar to what HK described. They are supposed to come on with a dim setting at dusk for several hours, then go out until motion is detected at which time they come on with full brightness.
Mine often stay on during daylight which I believe is due to their being under porch roofs and not enough natural light to satisfy the photocell. There should be other settings (like dusk to dawn-which might have the same problem-- or stricly motion activated) available on a selector switch on the unit.

If you can provide the make and model number of what you have, perhaps we can find the instruction manual and provide better advice.