Another tip. Lydia and other companions don't level correctly*, so their stats will stay the same level as when you first met them. To fix it:
Tell them to leave your service.
Open the console and click on them.
Type "getav health"
Type "disable"
Close the console for a second or two.
Reopen the console and type "enable".
Type "getav health" again, the value should be higher than what it was the first time.
*Haven't checked to see if it was fixed by 1.3. Don't remember it being in the patch notes.
i found a bug, dont know if it was fixe on new patch,where lydia,will default her armor even if you give her better one,all you have to do is remove or add an item and she will imediatly go back to the higher rating one she was using before.
That seems to mainly happen when she's unloaded by the game engine and has to be reloaded. So it usually isn't an issue unless you tell her to stay somewhere while you're running around alone.
there is a limit to how much she can carry.
Drop items. Hold "E" to go into command mode, and tell them to pick up the items. There's no limit on how much junk they can pick up.
