Ok I have been having this problem for a while, so I will start from the beginning, my car fails to start in the mornings or after a period of longer than 12 hrs. or so. It started about month and 1/2 ago, thought it was just the battery since it was the original battery and it has almost 5 years worth of life, a friend gave me a new battery he bought I replaced it and the car had no problems for roughly 4 or 5 days, then it started again, I replaced the positive terminal, nothing, bypassed the capacitor in the trunk for the amp, made it worse (as the capacitor has almost enough power to start the car on its own), then went to a friend's house we checked voltage out of the alt. and we were getting right around 14.8v or very close to that, we stumbled upon something and thought it might be it, with the amp meter around the negative line, we jiggled it and the volts started to flux, so I replaced the negative terminal and upgraded the ground wire that goes to the shock tower with 4 gauge wire and still no prevail, also there is no draw when the car is shut off. I shut off my stereo everynight and it's not a shaker.

 

Have both the battery and alternator laod tested. There are a lot of issues with the S197's charging system. Read all about it with the "search" engine.

 

Load test came back with "excessive ripple"

 

Get a confirmatory test. Then replace the alternator. Sounds like a bad rectifier. "Ripple" can also destroy a battery.

 

You should have no measurable ripple.