Need charging advice

[Steverk]

been rebuilding my bike over the last couple of winters. I recently fired it up for the fist time and noticed the tach was not working. This led to some diagnostic testing that has led me to believe the alternator may be bad. Hear is what I have discovered;
field coil resistance= 3.9-4.0 ohm
stator = .6 Ohms across the 3 whites wire.
Voltage at green wire from voltage regulator (new EBay reg) = .1 volts with key on, BUT drops to 0 volts once bike is running.
So my question is, is the above alternator resistance measurement enough to indicate a bad alternator? Am I missing something else?

battery is new AGM and voltage is good.

any help would be appreciated.

[bikerphil]

Am I missing something else?

Yes, inspect the alternator wiring harness connector for melting or corrosion. It is located behind the fuse box mounting plate which is held on by 3 screws. Common problem on these bikes.

[Steverk]

Connectors are in excellent shape and I have cleaned all of them thoroughly. Both the resistance readings are out of range per the spec in the manual, but I don't know if that is enough to call the alternator or field coils 'bad'. I would have expected some charging, even if it was weak- nada. Additionally, I also tested all of the alternator wires for dead shorts- negative. I also tested the harness wires for continuity to check for a hidden break inside the insulation- negative.

[bikerphil]

Well, if the alternator is out of spec it may be the problem. If the new regulator from ebay you installed is a cheap China knockoff that may also be the problem. There is a test you can do to see if the alternator is actually putting out. With the bike running, take a jumper lead from ground and add it to the green wire of the field coil harness and see if it starts charging. This would temporarily bypass the regulator and you should see 15V output from the alternator if it is working.

[Steverk]

thanks I'll give the jumper wire test a shot. When doing this test, should the harness to the regulator be unplugged? Yes, the regulator is a china cheapo.

[bikerphil]

Leave the field coil plugged in and just tap in to the wire end of the plug with the ground jumper. Yep, I've had no luck with the Cheapo China regulators, every one I've tried was bad.

[Steverk]

Roger that. Thanks.

[Steverk]

Went through everything again last night with a buddy, and it appears that the stator is the likely culprit. Thanks for the advice and if anyone has a working stator, I’d be interested. I also posted in the parts wanted. I have a lot of spare parts for an ‘80 include a couple of parts engines.