wiredgeorge wrote:
loudhvx - You stated:
If the brown wire is about 14v, and black wire is zero, then the regulator is probably good, and you are losing voltage in the ignition switch, fuse box, or wiring. The path in question is from the battery-positive to solenoid to fuse to ignition switch to brown wire on the reg. Each of those points should be at the same voltage as the battery (while running with the battery at 17v).
Help me out here with a bit of clarification. I much appreciate when you make posts as they are informative. IF you have 14 VDC on the brown and zero on the black (ground), how could you have 17 VDC at the battery? Is this what you were saying in the part I quoted or did I misunderstand. Thanks in advance. wg
This is a very common condition when the wiring is old on a stock bike.
Assuming the regulator, rectifier, wiring, and switches are good, this is what normally happens: The alternator puts out as much current as it can. The regulator shorts out as much current to ground as it takes to maintain 14v on it's sense line. The rectifier rectifies the remaining current into DC and that DC gets routed to the battery. The battery voltage gets routed through fuses, ignition switch, and several connectors to finally feed the battery voltage to the regulator's sense line. There is no significant current in the sense line. Notice how it forms a feedback loop. The regulator controls the voltage to the battery based on the voltage it senses on the sense line. If the alternator starts to put out more, the rectifier puts out more and the battery voltage goes up. This raises the voltage on the sense line which in turn causes the regulator to reduce the current to the rectifier (by shunting excess to ground). This will then lower the battery voltage back to 14v. It happens so quickly you may not even notice a fluctuation on a meter.
As I said, the sense line uses very little current, so the wiring of the sense line will cause very little voltage drop. If the sense line were switched directly to the battery without any other devices connected, it would work perfectly. However, the sense line is not exclusively connected to the battery. The sense line is connected to the main circuit coming from the battery. This circuit feeds lights, ignition, and other accessories. This large current draw causes voltage to drop along the path (in the fuse box, switches, etc.) if the wiring is old and switches/connections are dirty. So here's what happens: Let's say the battery for a moment is at 14v. The path, through which the sense line is connected, loses voltage due to the high current load. Lets say the fuse holder drops 1 volt and the switch drops 1 volt. Now the end of the sense line at the regulator is at 12v. The regulator is tricked into sensing battery voltage is 12v. The regulator must therefore increase voltage output by 2 volts to get the battery back to 14. Since the battery is really already at 14v, the extra 2 volts will force the battery to now be at 16v. Notice the regulator is basing it's operation on what voltage it senses from the sense line to ground. Since it is getting an artificially low sense voltage, it forces a much higher battery voltage.
The same thing can happen if the ground connection from battery to regulator is faulty. This is less common (but not uncommon). This will have the same effect, generally speaking.
This whole problem is the same as the low-voltage-to-the-coils problem and is caused by the same type of condition, but in slightly different areas. The coils issue emanates from a slightly later area in the path.
This problem is why it is important to base system voltage readings from the actual negative terminal of the battery and not some other arbitrary ground point, and regulator voltage readings should be done at the battery's positive post. Anywhere else may be misleading. If a problem is detected at the battery, then voltage readings should be done along the path to the regulator to isolate the problem area.
Notice in snerffs case, I told him to verify the voltage on the brown sense wire on the regulator. This was to make sure the sense line was not losing voltage. It wasn't, so therefore, in his case, the regulator was sensing 17v and maintaining 17v. That is a bad regulator.
Notice when the sense line is losing voltage, the regulator is sensing 14v and maintaining 14v. That is a good regulator, but the wiring is forcing a false reading to the regulator. This causes a high voltage reading at the battery. This problem often misleads people into buying new regulators when all they really have to do is clean some contacts and/or restore some wires.
So if a reg/rec combo has it's output wire tied directly to the battery, why use a seperate sense line? That seems redundant. Well, it's because the sense circuitry of the regulator may use a tiny bit of current if it is hooked up to the battery all the time. This may potentially drain the battery. That's why the sense line gets disconnected when the ignition is off. Some reg/rec combos, however, are designed to use so little current they don't need a seperate sense line and "sense" the voltage directly at the output wire (which goes directly to the battery usually via the start solenoid). I believe the 1-phase KZ650 reg/recs do this (circa 1978, 1979). But I think Kaw went back to a sense-line configuration on later models because of possible slow-drains on those 650 reg/recs. There may also be an issue with charging batteries that are still connected to the bike with the no-sense-line reg/recs. Since the sense circuit is connected all the time, a large charging voltage may damage the sense circuit on the reg.
