19v Honda[FIXED]

Hello. Working on a Honda Accord with a 2.3l 4cyl (f23a). Car came in with a dead battery, on idle system voltage was 11.2v and falling and stayed there @ 2000rpm. The 4 pin connector blk/yel 12v, wht/blu 12v, wht/red 5v, wht/grn 12v (koeo BTW).
I got a used one and voltage hit 19v. I thought reg was bad and got the alt changed, same result. Could we be so unlucky that both have bad regs? Anyone seen this?

any dtc's related to Honda eld?? also what does the white/red wire do on a scope while idling the engine? its supposed to look like a 0-5 volt square wave and change with loads.

I clipped this from another thread about a Honda charging system. There's a link at the end with a very good explanation of Honda alternator controls.

Tyler wrote: Just posting up a diagram for anyone else trying to follow along:

Just FYI, the Alternator C signal is the only one you need to worry about for no/low charging problem. It's a steady 8V provided by the alternator to the PCM, which grounds that voltage when it wants to shut the alternator off for fuel savings. If you see around 8V on that white/green wire with no charging taking place, then you're good to put an alternator in.

The FR is supposed to be a 0-5V square wave signal which the PCM uses for idle speed control, and nothing else. Zero impact on charging rate. With the alternator unplugged, look for 5V on the white/red wire.

Check this article out if you want, does an amazing job of explaining the operation of these alternators:

opensiuc.lib.siu.edu/cgi/viewcontent.cgi...11&context=auto_pres

I don't see many over-charging complaints that aren't the fault of the alternator/voltage regulator. Like Cheryl, I was also wondering if you had an ELD code.
I'm interested to see where you end up with this one!

Sure sounds like your replacement alternator is junk. There's nothing in the field control system that I know of that can cause these alternators to overcharge. The PCM can only command these to charge less, not more.

Only other cause I can think of is an alternator ground problem. A quick voltage drop test from the alternator case to B- can rule this out quickly. If that's good, then I say go with a new alternator. I've had good luck with the ones we get from CarQuest.

Returned the alt and got a replacement and 14v baby. Now to sort out all the other craps that wrong with this car. Thank you all.

Nice. Thanks for the fix update! What brand of alternator ended up fixing it?

It came off another F23a engine.

Caritech wrote: It came off another F23a engine.

Gotcha. There was another thread on a newer Honda charging problem that took an OE alternator to fix, so maybe original is the way to go on these.