Charging Question

[hudson]

Hey gents, I have a 71 R75/5. It is not charging when I rev up the rpms. The battery is fully charged and holds the charge (it is an Odyssey maintenance free). Here is my testing results so far:

Rotor
Across slip rings 3.4ohms
slip ring short to ground good
Lift bottom/back brush off slip rings, idiot charge light goes out

There doesn't seem to be any ground issues in this rotor/charge light circuit, which I believe the regulator is part of. So if I am right about that, I can assume the regulator is good?

Stator
Stator winding between all 3 phase outputs is about .9 - all same reading
Stator winding (all phase outputs) short to ground is good

Testing for AC current with the 3 yellow phase output wires disconnected from stator. throttled the bike to around 3000 rpms, and if I did this right measured very low, like 4v Ac. Did I do this correctly? The wires are disconnected from the stator when testing? I think I read that these readings should be more like 15-20v AC. If that is case, assume the stator is bad, although the tests above on it were good? I am putting the probes on the 3 stator lugs with the wires disconnected, correct?

Thanks!

[SteveD]

Have you read this Hudson?

viewtopic.php?f=1&t=9791&p=118140&hilit=Ced#p118140

[barryh]

Testing for AC current with the 3 yellow phase output wires disconnected from stator. throttled the bike to around 3000 rpms, and if I did this right measured very low, like 4v Ac. Did I do this correctly? The wires are disconnected from the stator when testing? I think I read that these readings should be more like 15-20v AC. If that is case, assume the stator is bad, although the tests above on it were good? I am putting the probes on the 3 stator lugs with the wires disconnected, correct?

The 0.9 ohms between phases sounds close enough. I have a spec of 0.6 ohms on a later model but that might have changed and in any case measuring fractional ohms value is not at all easy to do accurately. I can't decide if the rotor would be energised or not if the stator is disconnected. What AC voltage do you get with everything connected up ?

Voltage between each phase and earth should be a lot more than 4 volts so something odd happening.

[hudson]

Steve - no I didn't see that thread, I am familiar with some of those tests, but that is much more, so I appreciate it. Everything hooked up was the 4V AC. Will do some more testing. Thanks guys!

[jimmyg]

Hey gents, I have a 71 R75/5. It is not charging when I rev up the rpms. The battery is fully charged and holds the charge (it is an Odyssey maintenance free). Here is my testing results so far:

Rotor
Across slip rings 3.4ohms
slip ring short to ground good
Lift bottom/back brush off slip rings, idiot charge light goes out

There doesn't seem to be any ground issues in this rotor/charge light circuit, which I believe the regulator is part of. So if I am right about that, I can assume the regulator is good?

Stator
Stator winding between all 3 phase outputs is about .9 - all same reading
Stator winding (all phase outputs) short to ground is good

Testing for AC current with the 3 yellow phase output wires disconnected from stator. throttled the bike to around 3000 rpms, and if I did this right measured very low, like 4v Ac. Did I do this correctly? The wires are disconnected from the stator when testing? I think I read that these readings should be more like 15-20v AC. If that is case, assume the stator is bad, although the tests above on it were good? I am putting the probes on the 3 stator lugs with the wires disconnected, correct?

Thanks!

I don't see in your initial assessment whether the RED charge light is illuminating when the ignition is turned on (engine not running). Please elaborate.

jimmyg

[jimmyg]

sorry for reading your post too quick. I see now that you pulled the rear brush off the slip ring.

Does the light stay illuminated when the engine is running?

[hudson]

Hi Jimmy - yes, the charge light remains on when engine is running. I tested the diode board - all is good. The rotor tested normal, 3.4 ohms on rings and short to ground good - lifted earth brush... light off and then lifted DF wire from stator... light goes out. The stator ohm tests are good as well, but not quite sure about the AC testing of it yet. From what I read, it is normal get around 3 VAC at the three phase (U, V, W) lugs with engine running, which was around what I was getting.

Last night I did a regulator test where I jumpered the wires of the regulator DF & D+ wires. Started the engine, started to raise rpms, the light went off. Turned off engine. Plugged wires back in regulator, started engine, raised rpms the light would not go out, but did flicker some. So would I assume this is a ground issue with the regulator?

[hudson]

Very frustrated here. I performed most of the tests recommended on the rotor, diode board, regulator & stator. Performed continuity tests on wiring to each part, ground and diode board to battery to ensure no breakage. Still cannot find culprit. So I pulled one component out at a time and replaced with a new one, bench testing the new one AND also the one I pulled - BOTH SETS TESTED GOOD. Even replaced the battery with a spare I had. Still no dice. The only thing I didn't replace were the brushes, but they have plenty of life and good tension on the springs that push them down. The charge light will still not go out - only will if I lift the earth brush up or disconnect the DF wire from the stator housing. The voltage to the battery will not increase.

I am almost certain it is not on the rotor side of the circuit, so the charge light, rotor, regulator to ground is good. That leaves the stator and diode board. A

LL 11 diodes are good, signal only passes one way. All wire connections are accurate and secure. But I am not getting 14 VDC at the D+ or B+ to earth on the diode board.

The stator ohm and short to ground tests were good. I started engine, throttled to 2500 rpms and measured AC voltage on the across each stator winding. The old stator was producing 3-4 volts. The new replacement is now just under 2 volts. The Bosch testing guidlelines state it should be around 3 VAC at 2500 rpms. I double checked the brushes were making good contact on the slip rings. The ohms between the 3 phase connections were good and short to ground was good. Each stator winding at the actual SOLDERING points tested good (since I had to resolder the new stator winding wires on the stator housing I figured I would check the solder points).

What am I missing? ugh!

[Bevans]

I don't know if you've sorted this yet, but I just joined the forum. I am just going through a major charging issue sort out as well. Your test of AC output is a good test, but you need to first put battery voltage to the DF terminal to "full-field" the rotor with te regulator disconnected. Basically that turns the alternator on to full output. You should get 15 - 20 volt AC at 2000 rpm measured from each stator coil terminal to ground, with the stator fully disconnected from the diode board. when you were only getting 3 - 4 volts output it was because the field coil (rotor) was only getting around 1 volt of excitation voltage from the gen light. with everything all connected up again, if you again full-field the field coil by jumping DF to battery voltage with the regulator disconnected, the alternator again should go to full output, around 18 volts DC (so only do this for a few seconds). As well as the stator ohm tests, test for open circuit to ground. A short to ground anywhere in the stator will show up as a very low resistance path to ground (and to the metallic stator ring).