I've read a few of the other threads on this, but I have slightly different symptoms so I wanted to post here for a second opinion before I went and ordered parts.

On my 2013 manual fit I was having intermittent symptoms where when driving my dash cam would turn off, then trouble light and airbag light come on, and then my radio shut down, then my dash lights, and sometimes power steering assist. I took the battery out had it tested cleaned all the connections and replaced the battery with a 51r. I didn't have any more symptoms for a long time, but it came back again less noticeably recently where only the dash cam was shutting down. I finally received the voltage monitor that I ordered for the cigarette lighter a couple of days ago. What I've observed is that voltage is always between 14.1-14.4 until I hit 3700rpm. At this point and anywhere above voltage drops into the 13s and then into the 12s and then high 11s. If I sustain the high rpm basically 120km/h or higher in 5th the symptoms start and eventually I suspect the battery starts to lose reserve and then things start shutting down. Then I slow down and it starts charging again.

I don't regularly drive that speed for my commute because of the traffic, its the odd occasion where I'm driving a longer distance or out .Thinking back almost all of the times I had the symptoms was during or right after a long highway drive.

I can reproduce this voltage drop every time, and it doesn't seem to matter if I have the lights, heater, defroster on. The voltage falls off the instant I go above 3700.

I'm suspecting the alternator, but wanted to know if perhaps it could be the ECM, ELD, or any other things I should be checking before I order an alternator, throw it in and see that I still have the same problem. I only have 93k km, so it seems a little early for an alternator, but I guess if its defective its defective.

 

Yep that is the alternator. ChrisFix (awesome youtuber!) shows similar symptoms of voltage dropping when over a certain RPM in his how to replace video. He also has a how to test your alternator video.

 

Thanks for the confirmation. I put a new alternator in today, and problem is solved. The alternator change was surprisingly easy, the hardest part was replacing the serpentine belt.

 

Glad it worked out for you! Was the new alternator the honda part or an aftermarket?

 

It was an aftermarket alternator, Honda wanted some crazy amount for the OEM mitsubishi alternator. The lady at the parts counter laughed when she saw the price. I ordered it online and it was shipped to my door everything in for around $195. I was impressed that it even came with a report of the alternator's bench test. I didn't have to send back my core, so I'm debating tearing apart the old one and figuring out exactly what went wrong with it and fixing it if its reasonable. May keep it on the shelf just in case or sell it. Any tips or resources for that would be appreciated. I'll post back once I get it apart.