Test OK, but no voltage

[Glenardo]

Well the newbie w/ a new bike has his 1st problem. No Voltage above 12v.
Here's what I tested:
Test at idle = 12v
Test batt above 3000 rpm = 12v ( w/ & w/o lights on)
Ylw and Brn at rectifier = 6v, Red = 12v at idle. ( 3000 rpm = 12v)
Disconect Ylw and Brn = no volt on wires, but 6v on rectifier terminals.
A-ha!! Bad rectifier!! But I remove and test rectifier and it test good. Diode test from Ylw to Red, Brn to Red, Ground to Ylw, etc... But still getting 6v from Red to Ylw and Brn terminals.

Disconnect Ylw, Brn and Pnk wires in harness and no volts from alternator. Check continuity between all leads and leads to ground, etc.. = OK.

So I'm thinking I have a faulty rectifier that test good w/ meter but is allowing higher voltage to back feed and a bad rotor and/or stator. My "Glenn's Honda" manual says " A weak magnet can result from a defective rectifier which allows battery current flow back through the stator coils in a direction tending to demagnetize the rotor." I stuck a screwdriver tip onto the rotor and it has a magnetic pull, but how strong is strong enough???

Also when testing the Alt output on the Ylw, Brn, Pnk wires in the harness. Shouldn't I be testing it on AC on my meter ?? If so, do you test it to ground or how???

Any comments, questions, similar experience, advice?????

Thanks!!

[e3steve]

...... Also when testing the Alt output on the Ylw, Brn, Pnk wires in the harness. Shouldn't I be testing it on AC on my meter ?? If so, do you test it to ground or how???

Thanks!!

Have you checked the brown, yellow & pink connections at the main motor junction, just above and aft of the upper crankcase?

Disconnect them from there and check the AC voltage between bn & y then between bn & pk. The alt is galvanically-isolated from ground, so you'll get no readings between the three alt wires and ground; at least, not with the alt dis'd from the rectifier.

ACV should read somewhere between 18 & (maybe) 30 when revving the motor.

Let us know the readings.

[Glenardo]

That's where in the harness I was checking the voltage last night , but I was using DC. Woke up ( too early) this morning thinking that I should be checking it w/ AC.

Now I'm getting 18 -20 vac at idle and up to 40vac as I increase the rpm. That's on both leads to Brn.

So safe to assume the Alt is ok??? And the problem lies in the rectifier??

PS After adjusting the clutch the neutral switch is now out and I have a stripped screw head on my points plate!! ( old JIS ) You guys didn't tell me how much fun these bikes are!!!

[e3steve]

That's where in the harness I was checking the voltage last night , but I was using DC. Woke up ( too early) this morning thinking that I should be checking it w/ AC.

Now I'm getting 18 -20 vac at idle and up to 40vac as I increase the rpm. That's on both leads to Brn.

So safe to assume the Alt is ok??? And the problem lies in the rectifier??

PS After adjusting the clutch the neutral switch is now out and I have a stripped screw head on my points plate!! ( old JIS ) You guys didn't tell me how much fun these bikes are!!!

And you've only just started!

The alt is OK with that output, provided it has current also, but you'll need to load it to find that out.

Now reconnect the bn, y & pk, disconnect them from the rec and re-test between bn & y there and then the bn there and the y & then the pk in the headlamp bucket.

[mike1969]

For the neutral switch you may have pulled the wire connector apart when you were checking the alt. output. It's the green wire with the red stripe.

[Glenardo]

Reconnected the harness, disconnected Brn and Ylw at the rectifier. Getting 18vac on Brn -Ylw leads.
Checked Brn to Ylw and Pnk in headlamp, 18vac.
Rectifier w/ red connected and Br and Ylw disconnected, 5 -6 vdc on terminals.
Rectifier w/ Brn and Ylw connected and Red disconnected 15 - 30 vdc on Red terminal while motor running.

I keep going back to the fact that I'm getting 5-6vdc backfeeding thru the rectifier. That doesn't seem right.

I checked the neutral wire connection and it's the internal switch that isn't grounding.

I forgot to mention how I dropped one of the very small rectifier terminal screws last night and spent an hour on my hands and knees looking for it....

[e3steve]

Reconnected the harness, disconnected Brn and Ylw at the rectifier. Getting 18vac on Brn -Ylw leads.
Checked Brn to Ylw and Pnk in headlamp, 18vac.
Rectifier w/ red connected and Br and Ylw disconnected, 5 -6 vdc on terminals.
Rectifier w/ Brn and Ylw connected and Red disconnected 15 - 30 vdc on Red terminal while motor running.

How does DC the voltage, at the battery terminals, look when cranking 'on the button'? If it cranks healthily and the voltage doesn't collapse much further than about 10, then the batt is OK for now and not absorbing all the current from the charging.

I keep going back to the fact that I'm getting 5-6vdc backfeeding thru the rectifier. That doesn't seem right.

A good rec will block all DCV back to the AC i/p terminals, so replacing the rec is a good place to start. Let us know if you need pointers on improvement/replacement.

I checked the neutral wire connection and it's the internal switch that isn't grounding.

Pull the switch off and prise it apart; it's a simple design and (usually) simple to clean, re-tension and repair.

I forgot to mention how I dropped one of the very small rectifier terminal screws last night and spent an hour on my hands and knees looking for it....

The area of the floor under a bike/car/bench/desk/dining room table is notorious for eating stuff, isn't it?