Light sensor replacement

[msweig]

I have an exterior light that works based off of a light sensor (on at night, off during the day).  But recently I noticed that the light is on all the time.  My first thought was maybe the lens cover was just so dirty that it always thought it was dark, but after cleaning it that doesn't seem to be the case.  Just based on what the thing looks like, I think I know what part I need to replace it (but will verify once I take off the cover).  What I'm not sure of is what I need be be aware of/how I seal a plate that is outside (I've changed switches and outlets inside, but never outside). 

Based on the photos it appears the builder put something around the plate to keep water out, and it is obviously in pretty poor shape at this point.  What should I be using?  And is there anything else I need to be aware of?  I would imagine that any connections/wire nuts in the box you want higher in the box in case water leaks into it, then at least the water would be below the wires/connections.  Anything else?

[attachment=52964]
[attachment=52965]

[fredhargis]

Personally I would just use some silicone to seal it. I would be just as worried about insects of some getting there but it (silicone) will keep everything out.

[MstrCarpenter]

Just Google "120v photocell". You'll find lots of options. They're even in stock at the box stores. If the light is staying on all the time (assuming it didn't before) that's the culprit. It doesn't turn the light off, it uses light to produce energy to open the circuit. It's a normally closed (N.C.) circuit. And yes, silicone is good.

[msweig]

Thank you both!

Mark