Topic: New vs Old Regulator/Rectifier

[junruh]

Hello, I have a 1975 Honda CB 550F. It runs ok but I keep losing voltage while driving, thus losing spark,so I bought a new regulator/rectifier. Old one has only 7 wires, one of which was disconnected (it was the black one) . New one has 8 wires, one extra loose green wire. I will upload a pic of how the old one was hooked up and I have more pics if I need to send more. Thanks guys

[scottly]

Please post pictures of both regulators.

[scottly]

The proper reg/rect will have a red wire, a green wire, and three yellow wires in a single connector, which should plug into a matching connector on the bike. There should also be loose black, white, and green wires, which are connected to matching color wires on the bike.

[junruh]

1st is old
2nd is new

[scottly]

It looks like someone removed the red wire from the plug for some reason? Is the red wire still in the mating plug on the bike? Where does the red wire in the first pic go? The new reg does have the proper green wire.

[scottly]

There should be a loose white wire with a female connector from the bike, that the white wire from the reg plugs into. What's the wire behind the black wire in the first pic?

[junruh]

Yes for some reason the red is removed from the plug. The old one was plugged into a red wire that went directly to the positive side of the solenoid (not in the back of the plug, but I think it could be). Good to know the new one looks right. The black wire on the reg/rec side of the first pic is black all ghe way to the reg/rec. there is no independent green wire on the old one. Or are you asking where it goes on the bike side?

[scottly]

You need to find a white wire on the bike side for the regulator white wire to plug into. Without the white field wire from the bike connected there is no way the charging system can work. It should be near a loose black and a loose green wire.
The red wire from the bike will still need to be connected to the red wire from the new rectifier, so unless it can be re-inserted into the plug, you will need to bypass the plug like the old one.

[junruh]

Just to confirm that I’m following you… the independent black wire should be connected to the black wire on the bike instead of the white wire being connected to bike black as it was before. And now I need to find a white wire on the bike. What will the white wire be connected to on the bike end?

[scottly]

The white wire goes down to the left side of the engine, under the alternator cover. It may have a connection along the way, but you are looking for the end up near the regulator. Once you find it, I can tell you how to test if it's properly connected at the other end.

[junruh]

Ok I’ll look for it. Hopefully will get a chance tomorrow. Thanks a lot!

[junruh]

Ok I have a white and a black for the independent wires. What about my green independent wire? What should it plug in to?

[scottly]

There should also be a green wire with the black and white wires. BTW, with Honda, all solid green wires are connected to a common ground, and all solid black wires have 12V when the key is on.

[junruh]

Common ground… is that just like a normal ground? Or something that needs to be attached to a specific ground wire? So if I can’t find the wire I can run a wire from the ground bolt (underneath my seat that is attached to the frame) to my independent green?

[Bodi]

Every solid green wire (no stripe) is "ground" - the frame, engine, and battery "-" are all "ground" and there's a connection to the harness green wires somewhere. A wire terminal on a fastener into the frame.
You show a reg/rect harness of sorts but not the actual device.
The three loose wires shown connect to the bike harness, to the 3 wires that went to the OEM regulator. They are key-on power in black (all solid black wires are key on power), ground green, and field coil output white.
The plug is for the OEM rectifier. It plugs into the harness instead of that rectifier. 3 yellows (alternator output), red (to battery "+"), and green (ground/battery "-")
The other end of your harness is, I guess, the reg/rect module.

No other wiring is required. Assuming the harness hasn't been butchered of course.
The alternator output and field coil power wires connect through the engine plug. The second field coil wire has to be grounded, might be inside the engine or through that engine plug to a green wire. Both acual wires from the coil are white I believe, coil polarity doesn't matter.

One thing you can look at is the alternator wiring under the engine cover. There are bullet connectors in there that go bad partly because of the heat cycling. Also the contacts in the engine plug.

[junruh]

Got the harness plugged in. Ran my own ground wire to the frame. Moved the red wire to the center in the new plug and put the old red bike wire into the unused hole on the bike plug. Now I have black to black, green to ground, white to white, plug all matched up. Working on my tank this weekend, so I’ll try to put an update back on here later as to whether or not this all worked and fixed the problem. maybe it can help someone else:) Thanks guys, y’all are fantastic!

[Bodi]

Just for clarity:
The 3 yellow wires are the 3 phase AC output from the alternator.
The "stator" output coils are arranged around the alternator rotor (also the engine flywheel) and you can see the coils of wire on it.
The field coil is attached to the outer alternator cover. It doesn't look like much, really. Put DC battery current through it and a magnetic field is created, with one end N and the other S. Which is which does not matter.
The rotor/flywheel is a bit tricky. There are iron pieces shaped to bend that magnetic field from along the crankshaft axis to across it. These are cast into a nonmagnetic alloy body. So when it spins the magnetic field poles alternate across the stator coils, generating electrical voltage.

Output power is dependent on the magnetic field, and that's created by field coil current. The regulator just looks at the battery voltage and says "too low? Turn field coil power!" or "OK? Turn field coil power off". As a rule there is no variable field coil power - it just switches fully on and off rapidly, many times a second on a fully charged battery on a ride.

The original regulator does have a partial field coil power function but electronic ones, no.