Charging System Malfunction?

COLIBI23

MEMBER
2017 TOYOTA RAV4
4 CYL
4WD
AUTOMATIC
141,000 MILES

Hello - I'm wondering if you can suggest some troubleshooting steps for my problem. Had some odd electrical things happening (dash lights flickering, infotainment system rebooting, car also stalling at a stop). I went to my local auto parts store, and they tested the battery and the alternator, both tested bad. Both were pretty old, so I wasn't surprised. Replaced both. First two days everything was fine. Third day it almost stalled at a stop, then at subsequent stops though out the day it almost stalled, and the Charging System Malfunction light would come on for a split second then go off. During that split second the power steering would cut out then come back, and the infotainment system would reboot. I went back to the auto parts store and had the battery and alternator tested again, both tested as good. Just to make sure, I did the tests at home with my multimeter. Tested out as good. I also made sure all connections are tight and don't have corrosion.

What do you suggest for the next steps?

Thanks for your help - Jeff

Wednesday, June 11th, 2025 AT 8:52 PM

6 Replies

JACOBANDNICKOLAS

MECHANIC
110,136 POSTS

Hi Jeff, the idea that you have components rebooting and an alternator light flashing at times leads me to think there is a poor connection at some point, and not an alternator issue.

Have you followed the ground wire from the battery to where it mounts on the engine and body of the vehicle? Also, you tested the alternator with a multimeter. What was the voltage when the vehicle was running?

Let us know. At this point, it does sound like a failing ground simply because of the number of things that are affected. They are all on different circuits.

Let me know as much as you can.

Take care,

Joe

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Thursday, June 12th, 2025 AT 8:19 PM

COLIBI23

MEMBER
4 POSTS

Thanks for the suggestions Joe. I will check the grounds and test the alternator with my multimeter this evening and let you know the results. Thanks for your help - Jeff

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Friday, June 13th, 2025 AT 8:46 AM

COLIBI23

MEMBER
4 POSTS

Hey Joe, I checked the ground from the negative battery cable to the body, and it's tight. It's very easy to see and check. I then did battery, and alternator checks with a multimeter. The battery checked out good. The voltage when the car is running is 14.4 volts.

I then found instructions on how to do a voltage drop test, which consisted of running the engine at around 1500 RPM, connecting the positive lead of the multimeter to the negative battery terminal, connecting the negative lead to the alternator case. The voltage was around 23, and it looks like it should be around.2. I made sure the multimeter was on DC, and checked the battery again, and the readings were correct, so I think that 23 number is correct (it just seemed so high I thought I was doing something wrong).

I then connected the positive lead to the alternator terminal, and the negative lead to the positive post of the battery, and it read 131 volts!

Both of these numbers seems way too high, but I think I'm doing the tests correctly. I did them multiple times.

So, assuming these numbers are correct, does this tell us there is a problem between the alt and the battery, maybe a bad cable or corrosion?

I looked at the positive cable from the battery, and it splits into two. One goes to the starter, one goes to the fuse box. The cable from the alt goes behind the engine and then I can't easily see it.

Tomorrow when I have more light I'll trace the cable from the alt to and see where it goes. All cables have conduit around them, so I'd have to remove that to actually see the cables.

Thanks for your help - Jeff

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Friday, June 13th, 2025 AT 6:49 PM

JACOBANDNICKOLAS

MECHANIC
110,136 POSTS

Jeff,

I'm not familiar with how you are checking it. I know that if you use a multimeter on the battery, you can confirm the charging status. Normally, it is between 13V and 16V with the engine running.

It sounds like you are bypassing any voltage regulation. Otherwise, that voltage would have burned up the things.

Have you tried scanning the vehicle to see if there are any codes present or pending? Since this is a 2017, you should scan the entire CAN bus. CAN stands for Controller Area Network. The charging system utilizes CAN communication, so if there is an issue, a corresponding code should be displayed.

Here is a link showing how it's done:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Also, try this test:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Check that out and let me know your thoughts.

Joe

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Sunday, June 15th, 2025 AT 9:02 PM

COLIBI23

MEMBER
4 POSTS

Thanks for your help, Joe. I ended up tracing the wire from the alternator to the battery. It was wrapped around the back of the engine and took a while to trace. It is also encased in plastic tubing. I noticed a hole in the tubing, so I cut around it and it looked like a mouse, or something was nibbling around it. The cable had corrosion on it. I ended up enlisting a friend and we replaced the cable. After that, the car is running much better. I don't want to say it's 'fixed' yet since it's only been a day, but I haven't experienced any of the symptoms yet. I didn't drive it much yesterday; I'm going to drive it a lot more today. Thanks a lot for your help. I see you have a YouTube channel, I am going to subscribe, and I'll also make a donation. It's great that you are helping people like me out. It is greatly appreciated - Jeff

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Saturday, June 21st, 2025 AT 9:38 AM