[FIXED] 2004 Honda Civic 1.7 not charging

Got from another shop that installed a new battery, alternator and belts. First thing we noticed was a check eng light with a p1289 code for the edl also no battery light with key on or engine running. Tested the edl and it was bad. Alternator puts out no voltage. Tested battery cable to alt. Has 12v and passed volt drop test. Same with the ign feed wire to alt. Now with the connector at alt unplugged I show 12v on the feed wire, 5v on the fr wire, 5v on the L wire, and nothing on the control. Plug it in and start car. If I back probe connector I have constant 12v on feed. 2.42v on the fr wire, 11.42 on the L wire and 0.78v on the control wire. Nothing changes with load or speed. I can run a test light to ground and back probe the L wire and the light on the dash lights up but other wise there is no battery light. I guess I don’t understand why the L wire has 5v unplugged and 12v plugged in? I feel like the voltage regulator in the new alt is faulty but I guess is my control voltage normal. I would have thought it would of been higher and changing with load but it never changes while running. I repaired the faulty edl but that made no change to alternator other than I no longer have the code for it.

Has 12v and passed volt drop test. Same with the ign feed wire to alt. Now with the connector at alt unplugged I show 12v on the feed wire, 5v on the fr wire, 5v on the L wire, and nothing on the control. Plug it in and start car. If I back probe connector I have constant 12v on feed. 2.42v on the fr wire, 11.42 on the L wire and 0.78v on the control wire.

Grabbed the wiring diagram for reference:



The .78V on the control wire is the a big red flag, IMO. :ohmy: That circuit should have 8V or more with the alternator plugged in, engine running and low charge rate NOT commanded by the PCM.

I'd definitely check the ALT CTRL scan tool PID with the engine idling and loads off. If it shows the low charge rate commanded, then you'll need to dig into why. If it doesn't, then there's either a short on the control wire, or your new alternator is bad.

I'd also voltage drop the alternator case with the engine running.

Thank you. That’s where I was at with it before stopping for the weekend. I tried grounding the alternator case but that didn’t change anything. The control wire really bothered me as well and after checking it back to the pcm I was fairly certain The problem was in the new alternator like you suggested. Installed a new alternator and everything was back to normal.