Shuts down on external power, runs fine on battery.
Macbook Core Duo 13" A1181 (820-1889 logic board)
On battery power my Macbook runs normally. With magsafe connected, no light appears on the plug and the battery does not charge.
With the battery removed, magsafe plug shows green led and machine will boot from cold and run for about 15 mins, then shutdown. Restarting immediately results in a shutdown during or just after the chime(!).
However, removing the magsafe for a few seconds and replacing allows about 2 mins before shutdown, and disconnecting for longer periods before restarting gives longer run times up to a maximum of about 15 mins.
Thinking at first it was a temperature issue, I have done the following:-
complete strip down and cleanup;
new thermal paste;
replaced heatsink (old one had cracked board at the sensors);
renewed and re-routed the heat sink temp sensor leads;
HD check and repair permissions;
Also tried swapping in known good magsafe board and battery connectors from a working machine, and running with all ancillaries disconnected.
iStat reports normal temperatures throughout, and the shutdowns happen no matter how many programs are running, or how much the processors are working.
Is this a good question?