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Honda CB750K5 Restoration by Royhall
royhall:
I have no voltage whatsoever at any of the yellow wires tested at the re/reg plug either yellow to yellow, or yellow to earth. Does that mean that the alternator is done. Think it's time to get the alternator cover off and have a look.
AshimotoK0:
--- Quote from: royhall on October 03, 2023, 03:18:36 PM ---I have no voltage whatsoever at any of the yellow wires tested at the re/reg plug either yellow to yellow, or yellow to earth. Does that mean that the alternator is done. Think it's time to get the alternator cover off and have a look.
--- End quote ---
If you have decent resistance readings between yellow wires then the stator is probably OK, provided no leakage to the frame. You do need current in the field coil though to magnetise the rotor on the crank, which is controlled by the regulator.
royhall:
The field coil resistance is 8 ohms on my meter, should be 7.2 but again take the leads 0.8 away and its correct. When I turn on the ignition the black wire on the rec/reg should give battery voltage then the white wire should go live to the field coil and then to ground. If that is correct I can test for voltage at those points (basically white to field coil goes live on ignition switch turn on). Am I correct with this? Thanks all for the help. As you probably guessed, this is a school day for me.
Bryanj:
Check that the green wire from field coil goes to earth then temporarily connect white to battery positive then disconnected yellow wires should give the ac volts between wires THERE IS NO CONNECTION TO GROUND on this system.
If you dont get ac volts chances are the connectors at generator are bad
royhall:
UPDATE: I have 12.83 volts at the battery. With ignition on 12.80 volts goes to black wire on the regulator, but no power on white wire out of regulator to field coil. Two possibilities, either the rec/reg is duff or the regulator is seeing 12.80 volts as a fully charged battery and has turned off the charging circuit. Now if only I had a duff battery with 10.5 volts to give that a try. No idea how you would test for that. I'm fairly happy that the stator and field coil are okay so can possibly reassemble it tomorrow. I suppose I could run the engine with lights and indicators on to drain the battery to below charging level and see if it cuts in.
MODE3(seeFig.3). Battery voltage is excessively high; ignition switch is closed (on). The regulator’s lower set of contacts are now closed. The current paths are: From positive battery through fuse and field resistor, through the closed lower contacts of the regulator and then to ground. No current goes through the field (0amps), and the alternator has no output; therefore, no rectifier output and consequently a lower battery voltage.
The above could be happening due to a fully charged AGM battery and there is no actual problem with the charging system? I'm thinking 12.40 volts is the field coil switch on point. I may be doing all this for no reason, except a good learning day.
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