outdoor lantern lamp with pir sensor,won't switch off.just dims?

i have an outside lantern which blew a bulb.i bought a new bulb & now the light just dimms,it does'nt switch off.when the sensor picks up movement it comes on bright as it should,but always goes back to a dim light.i know some of these lamps do go dim but this one never has before & the light is wired up permant with no interior switch so it never goes out even in the daylight.the only thing ive noticed is on the bit where you screw the bulb in it says max 1 amp.im not sure what amp the bulb is ive just put in & no bulbs say what amp they are,just what volt & watts.would putting a bulb in thats more than 1 amp cause this to dim instead of switching completely off?this light hasnt got a dimming feature on it either,all ive got on the back is a time screw for how long its supposed to stay on for before it goes off & a screw for light & dark with a moon & a sun on it.help