2005 Toyota Prius - I think I need an alternator

I think I may need a new alternator. Aux battery keeps dying. Looking for a local shop that works on Priuses.

I know of one in Anchorage , Alaska . Is that anywhere near you since you did not say .

Prius , might be best to use a dealer .


Here is a story that may get your started: Car Talk’s Ultimate Guide to Finding a Good Mechanic in 2023 - Car Talk


I’d find a mechanic that knows the Prius, either dealer or an independent shop that has that capability. From what I can tell, it doesn’t have an alternator, the 12V battery is charged using a transformer from the high voltage system. So your problem with the 12V battery has some other cause than a bad alternator, it seems.


Concur w/above, make/model doesn’t seem to use alternator. Problem is likely either low-voltage charging system has failed, or aux battery is old, worn out, and won’t hold a charge. Probably the latter. I expect the Prius requires a special type of low voltage battery. If replacement needed, double-check the shop installs correct battery type for the car.


No alternator used on that car.

Any idea how old that 12V aux battery is? I imagine it should have been replaced twice by now and is due for a third one. Or perhaps there’s an electrical drain that is killing the battery.

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Thank you! So cool that I got replies so quick! I appreciate you guys so much!!

Battery not that old, a little over a year. I was taking things out of the trunk in my garage and forgot to close the driver door. Then I was sick for two days and I guess the interior lights ate the battery as far as I can tell. I can get it started but once I turn it off, it does not come back on without a jump. None of my local guys want to touch Priuses because the electrical system is complicated and our local Toyota dealership is insanely corrupt. Is it possible that I just need a new battery?

Yes, but seems unlikely cause since you say battery is less than 2 years old. Imo you need a pro-assessment of the battery and charging system. This sort of job usually wouldn’t require a dealership. Ask your Prius-owning friends, co-workers etc which shop they use.

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What are you basing that statement on ? Actual experience or rumors . How far to the next dealer ?

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The battery should be recharged, then tested.

If you purchased the battery from a Toyota dealer, the battery comes with a 2 year free replacement warranty.

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Actual experience. They have had to restructure because of criminal activity and from what I understand, it is just the same owners and the reviews pretty much reflect that not much has changed.

Thanks, I am going to just take it to Pep Boys. I called them and they did not seem terrified when I explained the problem.

Little far from Staten Island, NY but I will keep you in mind if I get out there. :slight_smile:

Thanks! I have no Prius friends in the area but I should ask someone at the local car service. They have a fleet of them. Hadn’t thought of that. Cheers!

Here is my only experience with Pep Boys.

My father-in -law had his car towed to them because it was bucking and jumping when he tried to start it. He took it there because they had mailed him a coupon.

My wife had picked him up and brought him to our house to wait.

Pep Boys had called our house to tell him that they had replaced his starter 7 times !!! and it was still doing the same thing. I had just gotten in off a trip and was going to bed when they called.

I took the phone and asked them if they had checked for a cracked flywheel while the starter was out and they told me they did not know how to do that because they did not replace flywheels.

If you do wind up at Pep Boys, I would love to hear of your experience.

He had it towed across the street to the Chrysler dealer who charged him not much more for replacing the starter and flywheel on his front drive car than Pep Boys wanted from the starter.

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I have a very good local guy but before that, I did go to Pep Boys a few times and never had a bad experience. Never complicated issues before. I hope this is not complicated but when I jumped the car tonight to go home, the brake light, the ABS light and an Exclamation Point light came on and stayed on so we shall see. I will update at the end.

The exclamation point is the hybrid system warning light. You need to find a hybrid mechanic, not Pep Boys.

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The exclamation point inside a triangle is the master warning light, it is on because the ABS light is on. The exclamation point on the outline of a car is the hybrid warning light.

The ABS light is probably on due to low battery voltage.

I’ve had both good and bad experiences with them. The main issue with a shop like Pep Boys is that they tend to have young employees without a great deal of experience. You may have friends or neighbors with hybrids that aren’t Toyotas and Toyota builds a lot of hybrids other than the Prius. Maybe they can point you to an independent shop with the tools and experience to do the job. My repair shop has hourly rates similar to a dealer, but they have experienced mechanics. I’m willing to pay for top quality diagnosis and work.

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