trouble shooting, maybe alt

[wsladaritz]

Looking for a second opinion, ideas, or someone to just point me in the right direction.

Initial symptom: Fiance tells me that the radio went off and came right back on while she was driving my car. It sits all weekend because I'm busy with other stuff. I try to crank it Monday morning just to see what happens. Everything comes on like normal when it hits ACC position. Nothing but dimming lights when turned to crank position. No noise or anything. Check the Capacitor because it has a led voltage read out. 8ish V

Today used some jumper cables and cranked okay. Voltage reads 13ish V. Every few minutes the radio & 2 amps turn off for a second and come right back on. The voltage drops to about 9V each time this happens. Car keeps running during all this. After about 20 minutes maybe (I wasn't keeping time, just guessing) I notice a pattern that this only happens when I hear the car rev up a little by itself. A/C is not on, so not sure why it does that, but I know it's always done that. I'm assuming it's the alternator kicking in maybe?

After I turned the car off, the capacitor was beeping at me again so I went to check the voltage display and it is back down to 8 something.

Car won't crank again, but all electronic components come on. So I'll have to jump it when I have time to get back to this project.

The battery is an Optima yellow top, possibly 2 years old or getting close to it. Everything else in the engine is stock. I am going to get a wire brush tomorrow and try cleaning the battery terminals, see if that changes anything. I live in an apartment now that doesn't allow any car maintenance in the parking lot so for the first time in my life I don't have a driveway I can spend all day figuring this out and fixing it myself I'm going to pay someone else to work on my girl...

Luckily I have a work car so the yaris is no longer my main mode of transportation but I'll be damned if I'm going to let her rot away!

I know we have some intelligent individuals still roaming around here. Any advice for me?

Thanks