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I have a 2015 Honda Fit EX. On my dashboard, there is a small screen that has been displaying "CHECK CHARGE SYSTEM" and displaying warning lights (TPMS, power steering, and stability control).

I took it in to a mechanic and they diagnosed it as a bad alternator that isn't charging the battery fully.

The alternator itself sounds fine (still quiet) and only has 50k miles on it, so I believe the bearings and the internals are still good.

Can I just change the regulator in this instance? When should you swap the regulator versus swapping the entire alternator?

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  • Its strange to have the alternator fail at such low mileage. Do you know if they do a proper battery load test?
    – race fever
    Apr 6, 2016 at 4:05
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    Shouldn't it be still covered under warranty? Either way, you don't know if the regulator needs to be swapped. A diagnosis is required.
    – I have no idea what I'm doing
    Apr 6, 2016 at 7:31
  • @IhavenoideawhatI'mdoing Not under warranty (it ended on that at 36k). I can't believe it failed that early either.
    – Kevin Evans
    Apr 6, 2016 at 14:42
  • @racefever By battery load test, is that the test where they check the voltage and the CCA output? They did test the battery separately and it looked fine (CCA exceeds spec, voltage is normal). I'll be doing a voltage drop test later today, as well as pulling the battery and having it tested elsewhere.
    – Kevin Evans
    Apr 6, 2016 at 14:42
  • Yes, and thats a good plan of action!
    – race fever
    Apr 6, 2016 at 15:59

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This sounds like a regulator fault. I sell these alternators daily, and we cannot get the regulator as a spare part (well, not here in NZ, anyway).

The alternator has a feedback terminal to the ECU. If it does it again, give the alternator connector a clean and see if it goes away. If it does, the issue is a loose connection. If it doesn't, then the issue is internal and you're up for a new unit.

The reason the other lights come on, is that the ECU recognizes that these items may fail if the battery is not fully charged. As the report is not coming back from the alternator to say that it is charged, the ECU flags a fault on those items as well.

Of course, the above assumes that the battery is in good condition. As the car is less than a year old, it would be pretty odd if the battery is faulty. A proper load test and off-vehicle charge should clear the battery of guilt.

When should you swap the regulator versus swapping the entire alternator?

When you know what has damaged the regulator in the first place and it has been fixed. If, for instance, the rotor has a short circuit and is drawing too high a current, the new regulator will fail also.

When it is a major job to extract the alternator for repair. If it's a 3 hour workshop job to get the unit out, you don't want to do that twice. I believe the Honda is not that hard, so it's really a call to be made from your wallet ;)

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