Making sound every fifteen seconds, even after powering off (225K miles)

This is a sample of the noise:

This noise has been going on for a long while, but the car seems to drive fine. All of my dash warning lights came on a few weeks ago. I drove to a Jiffy Lube and they said it's not returning any codes. But the car wouldn't go into drive. So I disconnected the rear battery to reset the codes. It still seems to drive fine. No codes since.

I bought an OBD reader and used the Dr. Prius app today. No codes. I tested the battery and it says 45.5% capacity left.

I've been the sole driver of this car since 2006. I've felt it struggling recently, so no long trips anymore. I've really only ever done oil changes for maintenance. I did some recommended maintenance stuff around 125K miles. Recently, the AC stopped blowing cold air, but it's winter so I've been putting off getting it fixed.

I don't know if I should begin going through the steps of maintenance and repair or if it'd be better to put that money toward a new car. I'd hate to say goodbye to Ole Reliable "Suzanna," but I also dig the new model.

Any help or advice is greatly appreciated!

 

Thank you all for replying and helping!

I'm in Central California. I didn't expect it, but if anyone can help or knows of any good mechanics, I'd greatly appreciate it! I'm up to drive anywhere in the state and would pay whatever it costs.

I haven't needed to do any DIY repairs outside of changing headlights or small things and this is the only car I've ever driven, so I don't have any real DIY knowledge for cars. I've looked into other posts here detailing setting up the Techstream and replacing the brake actuator. A repair that large is absolutely beyond me. But I can definitely at least clean that HV battery fan and white connector. I'll do it this weekend!

I don't have a multimeter, but I can go to a mechanic to have it checked. The 12V is about 3-4 years old. I'm checking out videos on changing transmission fluid now.

There's such a wealth of information on this forum! I've already looked through more than a dozen posts about maintenance, replacing the brake actuator, and more. I'll continue reading.

My brakes seem to work fine. I've had to make sudden stops even recently and there weren't any issues. I had some brake work done on them at around 150K miles I think. I can't remember specifically what it was. I think it was the brake pads?

I've made several long trips within the last couple years and haven't had any issues with the car. I drove up to Sonoma (~400 mile round trips) a few months ago and it drove perfectly except that's when the AC went out on me.

The AC just isn't blowing cold air, so I'm hoping it's as simple as just refreshing it. The summers here are brutal, so I wouldn't be able to live without it.

Do you think I should begin calling local mechanics to see who may be able to fix the brake actuator, or is it something that's just repaired by dealerships?

Thanks again for all of your help! I was really hoping to get to 300K. I love this car. I've driven cross country a couple times, throughout Canada, long trips all over, I even toured with my old band in this car. Lots of good memories.