Won't start but battery is fine—any similar experiences?

[IceBlue]

I have a 2007 9-5 Aero with approx 130k miles. This morning I started the car twice with no problem. After the second start, I parked and went to my house to retrieve a couple of items. I was away from the car for less than 10 minutes (probably less than 5) and when I tried to re-start it, it would not start. It seemed like the battery was very low but, again, it had started twice with no problem earlier the same morning (the first two starts took place inside of 1 hour). I called AAA road service and they sent a guy to give me a jump. He did a diagnostic and pronounced the battery to be in 100% perfect condition. However, after giving me the jump, he had me turn the car off and, with the ignition turned off, he got a reading indicating that the battery was discharging 3 amps (not sure if it was per minute or per hour, or what). We checked to be sure that no lights or anything were still on and they weren't. The car was turned off and the key was out of the ignition. After the re-charge, I drove 100 miles and the car has now been re-started 3 times and everything seems normal but clearly something is amiss. Any ideas?

[phoenix]

Starting when cold but then not starting when warm is usually a symptom of a faulty crankshaft position sensor. As the engine warms, the resistance increases. The intervening time between calling the AA and him arriving could have been enough to allow things to cool and it provide a valid reading again. if you have access to a multimeter (or even buy a cheap one for a fiver from eBay) that measures resistance, the CPS should be about 900 ohms cold. Much more than that and it needs replacing.

You have a to wait a minute or so when doing readings of battery drain for things like interior lights etc. to all switch off.