oil light

My 99 Disco II's oil light started coming on about a week ago.  The light comes on when accelerating and usually goes off at idle.  I changed the oil and filter and the light is still coming on, but there is not odd noises or temperature changes.  I am wondering if it could be the switch or if there is perhaps some type of screen in the oil pan/sump that may be getting clogged.  If so, I would like to pull the sump off and check it out.  I have the shop manual, but I wanted to know who has performed this and what should I look out for.

There is a screen on the oil pickup tube. I would suggest flushing with tranny fluid before pulling the pan. You will get a lot of gunk out, especially if you are pulling the pan.

After that, if it still comes on do a mechanical oil pressure test both at idle and at 2000 RPM's.
Mike

Can you point me to somewhere that describes how to do the flush? 

Drain your oil, fill with ATF, idle for 20 minutes. DO NOT DRIVE. drain ATF, pull your pan and clean everything out. Change filter and add new oil.
 
I say again do not drive it with ATF in it. Just let it idle in the driveway.

Thanks everyone for the help.

Mine was doing kind of a similar thing after I did the trans fluid flush. (Think I loosened up some crud?) Seemed like the oil light came on after it had run a few miles, sucking up crud from the bottom of the pan that had been loosened from the flush? Anyway didn't test it out too much, parked vehicle and pulled pan ASAP. Pick tube is right there, two bolts. Use Berrymans B12 to clean, will disolve the crud in seconds....Good Luck!