Charging System problem

[Dave]

Hello,
I need input from any one could help me to diagnostic ma charging system problem. Here is the situation; one morning when I started my 03 Civic LX the Charging System Indicator came ON. The Voltage was at a constant value of 10 V instead of as usual approximatively 14 V (I have a voltmeter always plugged in the cigarette ignitor). A couple of day after, I fully charged the battery and then start the car to perform a diagnostic of the charging system. I measured the voltage output directly at the alternator (voltage difference between the alternator housing and alternator positive stud) and got 10V. All electrical connections look fine. The fuses related to alternator are not blown. I conclude the alternator is bad.
I replaced the alternator (bought a new alternator on Amazon), recharged the battery and then start the car. Now I get a voltage of 11.7 V. It is still not working fine. Could anyone give me hints where I should dig to fix my problem? As a DIY I have no more idea where to look at.
Thanks a lot in advance!
Dave

Topic

[Richard Kirshy]

Possible causes:
1 You received a faulty replacement alternator ….( I purchased a new replacement and it turned out to be defective, so it is possible )
2 Assuming proper installation, Faulty wiring … poor ground or damaged wiring or connector out of the alternator.
3 Missed a blown fuse.
4 Faulty wire at the fuse connection.
5 Bad battery terminal.
6 Slipping belt
You did not mention if you have any indicator light on your dash.

[Frank Heiser]

I believe on those Hondas the ECU is involved in regulating the alt’s output, might be a wiring or ECU problem. And I would take that alternator to a Autozone or similar and have them test it to make sure it is good before you go chasing ghosts elsewhere.

[hondaguy453]

What is the batt voltage with the key off, engine not running? It’s also recommended that you replace the batt whenever you replace the alternator.

[Dave]

First of all thanks everyone for you input!. The battery voltage when the engin is off is 12.3V. The battery seem to be good but I will have it load tested to make sure. Meanwhile I spoke with a friend of mind who is automotove technician and he told me that the alternator positive stud is very brittle. It remind me that I had a strange sensation when I torque the alternator positive nut. I might broke it under during installation. I will dig into that. Thank again for your help! Dave

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