Bulb keeps burning out after a few days or when it rains.
Anybody have any idea what the problem is? It's meant to provide
illumination overnight.

Are you sure the bulb burns out and its not just the contacts getting corroded?

Are you sure its the correct bulb - could be overheating?

Both comments a bit wild - just thoughts.

Thanks for rely DD Yes, the bulbs are gone sometimes very
discolored, sometimes broken. I've wondered about contact
corrosion, it does look beat up and out in all kinds of
weather. I'm a little hesitant about cleaning or scraping
the contact as the lamp is wired direct underground.
The lamp runs on a light sensor. I've using 40w lamps.

Just a long shot. Are the bulbs the right Voltage. I made the mistake once of getting 110v halogens instead of 240v for outside security light. More likely to explode or blow immediately than burn out over day or so.
I find some cheap bulbs from far east for car indicator or sop lights don't last too long

Hi fish
No they are regular light bulbs (110v) here. Although they are
cheap bulbs. Don't have a problem using them inside. Also the
lamp post is about 25 years old. Hate to call an electrician.
About 70 pounds just for them to knock on the door.

Try halogen bulbs, your normal domestic indoor bulbs are not used to rapid cooling from outside temperatures which causes them to fail in no time. Try a halogen yep there six times the cost, but should be tolerant to outside temperature / damp conditions.

Halogen bulbs come in all shapes and sizes now, not just for floodlights.

Thank You Mark. I will keep that in mind. In times gone by the
regular ones would last for a year or more. I keep thinking it's
a corrosion issue.

Could be damp or water getting in causing a short, check around the seals, It should be connected to your fusebox, does it trip the fuse when it goes out? if it has no specific place on the fuse board it could be wired into the socket ring main circuit, has this been happening for a long time or only recently? try and remember when it started happening was it after you changed the bulb? how long did the previous bulbs last before this started happening, sorry I know this sounds like twenty questions, just trying to get an idea of what it might be.

It could be a vibration issue if the fitting isn't rigid?

hey casper
It started happening about 2 years ago, before that the bulbs
would last at least 1 year. The fuse doesn't get tripped.

@dd yes it's rigid.

I think I've found the problem. I just went out for another look.
It rained last night. Right away I could see water at the base by
the socket. I pulled up the brass cover and found the socket to
be well rusted. I cannot see how the rain is getting in there but
as they say if there is a way in, water will find it. So I think
I will look for another lamp to go on the post.

Thanks dd, casper and Mark for your help

Mark
Do you really mean halogens - or LEDs?
LEDs are the costly type but they do last a very long time and seem to be insensitive to any vibration effects. I am slowly changing all the GU10 halogens around my house to the LED type.

Snod