An alternator question

[JWSanders]

The alternator system on the 400 is a lot like the one on the 1100. 3 windings, each leading to the rectifier.

I just put a second rotor/stator on the bike, and still I get no charge. I have yet to change out the regulator or rectifier. Looking at a few on Ebay. The rectifier checks ok with a meter. I'm even considering wiring in the spare 1100 rectifier/regulator I have. It looks like it would be straightforward enough.

Shouldn't I see some sort of ac voltage on any of the 3 rotor leads when the bike is running? I have verified the field coil is getting 12V when the bike is running. I am not seeing either AC or DC of any sort either metering across the alternator coils or with respect to ground.

I ohmed out the coils on both stators and field coils and they are all pretty close to spec, being 1 ohm when it's supposed to be .7. My meter leads ohm out to .2 by themselves. Will a difference that small be too much?

Both alternator units measured almost exactly the same, which I why I suspect something else.

Any help would be much appreciated!

[randy]

The field coil is getting 12v, but is it creating the magnetic field? Field coil should attract a thin feeler guage with the key on?

[JWSanders]

I could not find my feeler gagues to see if it was making magnetism, but I'm betting it's not. All my stuff is in boxes and I don't want to trample my neighbor's generosity by emptying them all over his garage.

As it is, there is no voltage when the key is on. One wire of the field coil (brown) has 12V (direct from the fuse) on it but the other (green) has nothing.
When I remove the field coil, the voltage is floating around 4-6VDC. When it's running, I get the battery voltage on the leads. The green wire goes directly to the voltage regulator.

It's rather perplexing that they would be getting the voltage for the field coil from both sides (in parallel) from the voltage regulator (input & output), but that's exactly what they do, according to the wiring diagram.

I'm assuming (with all the required deference ) at this point that the regulator is kaput. A cheap one popped up BIN on Ebay today so I scooped it up. Hope to get it soon.

[Bob Falter]

You need to have some DC voltage across the field coil and then you should get some AC voltage from lead to lead coming from the alternator (not to ground).

Bob

[Geezer]

The way it works is the field coil gets power all the time from the brown wire and then the regulator grounds the green wire as needed to complete the circuit as needed.

If you're not seeing any magnetic draw to a feeler gage (ignition on but engine not running) then you have a problem.

Check and clean all the connections and check the resistance at the field coil again. If it's out of speck either high or low, it's probably fried.

Geezer

[JWSanders]

Turns out it was the voltage regulator.

Popped the replacement in and now have a decent voltage (13.25 instead of the 14 or so I'm supposed to) on the battery when the bike is running. It's charging, at least. Put 75 miles or so on it today and got back with a better charge than when I left.

Now I need to dielectric grease all the fittings, and clean up the ground lead to the motor. Thanks for the help guys!