I have a saab 9-3 2.0 aero convertible and all has been fine until today...

i jumped in as usual and put the key in to start and noticed i didn't get the usual "click" of all the electronics, but still turned the key to start... and all i got was a click..... click....

I noticed the display was reset and seemed as though the car had no power. I got the jump leads and connected to the wifes car and jump started my saab with no problems. I drove it around for 30 min but when i stopped, the same thing again!

i went to the motor factors and bought a new battery. without putting in the car i used the jump leads and tried to start the car off the new battery but again no joy. I noticed the battery was wrong one supplied (given a 480A / 56Ah). Went back and got a 640A / 70Ah and again it still wont start. Tried the jump off another car and starts straight away.

I'm stumped, can anyone help?