Help With Electrical Problem

Greetings all. I have a 2001 9-3 two door with an electrical problem I would like some help with diagnosing.

My son was visiting and took it out for an errand the other day and found it wouldn't start after shutting down and had to get it jumped twice to get home. Runs fine after starting.

So, car gets home and the backyard mechanic gets on the case. First thing I do is fully charge the battery to see if it maight be an alternator charge issue.

Battery back in car, turn on key and nothing, not even dash lights.

Hook up jumper cable to my Jeep with a big Optima battery. Lights come on then, but weak starter action, car won't start.

As soon as I unplug the jumper cables, lights go off on dash again.

So, I'm thinking it's the ignition switch or somwhere else that routes power around. What has me curious is why I get the dash lights on with the jumper cables but not on a fully charged battery alone.

Any help will be appreciated as to this diagnosis. If I get it running I know I can get it to the shop. It's a manual trans so rolling start is possible where I live.

Thanks in advance for your help.

Tom
Potlatch WA