Re: Overcharging Alternator (Delco 3 wire hook up)
He He -- if "at rest" means at idle speed, it's a different story.
Then: Need to know how the 17.5 amps was measured - was it the current in the alternator output line? If so, what accessories were on?
Once the battery is charged, the alternator still provides all the current to run the vehicle, including ignition, heter etc. That's normally around 8-10 amps - depending on ignition type and what's on.
As far as the battery running down fast, does it do that when it's disconnected too? If so, defective battery -- or possibly the top of the battery has so much conductive dirt on it that it's discharging it - if so, just clean it off.
Engine off - disconnect/reconnect the battery - see a spark? If so, something's on all the time. Sometimes it's a digital radio with the lighted dial that shows a clock - some draw way too much. I've had 2 like that.