T43p boots only with external monitor and lid switch engaged

[vice]

Just ran into a problem. I've been experiencing screen blackouts, so I figure it to be the LCD inverter going bad, or the cable shorting since I can hook up fine to external monitor. I've replaced both today, and when I turn the machine on I get some LCD and fan activity then it just shuts off after about 4 seconds.

So I plug into the external monitor, same thing! So I decide to hold down the lid switch and it boots right up. Tested with the new hardware, and old hardware as well. Also, while running with the lid switch engaged, once released the machine will shut off immediately. The only way to get it to boot back again is to remove and reinsert the battery.

What could be causing this?

[BillMorrow]

sound like it could be a defective lid switch..
do you have a high quality ohm meter..?
to test the functionality of the switch..