always runs on battery

Hi. Tried to find answer here, but couldn't.

Have a Dell Inspiron 1100. Adapter is fine because it works on another identical laptop using same electrical outlet. However, when I plugged it in today, I noticed the message that the battery was low, which didn't really register with me at the time until it went into hiberation after 2 hours.
I then realized that the AC power hadn't kicked it.

When I plug the adapter in and power it up now, only the battery light flickers, not the power light. (On the other laptop, the AC light goes on).
I made sure all screws were tight, and then tried running with battery removed, but no difference. I am trying to recharge the battery now to see if it will get enough juice to get it to turn on, but any idea why it won't power up or run under AC power? Thanks.

p.s. Shouldn't the battery charge while it's running on AC power, or only when it's laptop is off? Just a non-related general question...(just looking ahead to the time when the ac power issue is solved).

More than likely you need a board replaced. Had a similar issue with a 5150 a few months ago. If you're sure the a/c adaptor is good, then it's almost for sure the board that will need to be replaced, and I believe with that model, it is the entire mainboard.

One thing to try, plug the a/c adaptor in, and then wiggle the plug at the back of the laptop a bit to see if the a/c led lights up. Sometimes a solder joint will break loose, and wiggling it will make a momentary connection that you can see, so you can then crack the case and touch up the faulty joint.