HomeMade Voltage Rectifer, doesn't work???

We'll I just got back from the garage. I think this is round 87 or so of what is turning into a saga.

I checked the voltage rectifier again, all appears to be well except I'm not sure what I should expect in terms of resistance between the (+) and (-) voltage leads. I did get the same result as mentioned above again, however.

I did see that the voltage regulator does what it's supposed to do (excite the field coil) at least when the voltage is below 12v as it is now.


:dry:

The core of the stator is the metal frame of the stator. They want to make sure none of the windings is shorted to the frame. Do the continuity tests before going further.

The slip rings are the round metal contacts for the brushes to ride on. They are on the rotor. They are the contacts through which the rotor gets its power.

Let's ignore resistance checks on the rectifier since rectifiers are non-linear devices and the measurements are affected byu the meter itself. As a matter of fact, let's leave the rectifier removed from the bike.

With the rectifier removed, the regulator will put full power to the rotor. Which means the alternator will be putting out full AC power. Measure the AC voltage on each pair of stator output wires (they shouldn't be connected to anything since the rectifier is removed from the circuit). We want to see 30 to 70vac with a little revving.

Next, let's verify the voltage will indeed drive a load. The easiest way to do that is to use a 55w headlight as a load on each pair at a time. It should not take much revving to make the light bright. Be very very careful. It will be easy to blow the bulb if the alternator is working. Only briefly touch the wires to the bulb to make sure it's not going to blow right away. When you rev the bike (don't go above 2000 rpm) be ready to disconnect the bulb if it gets too bright.

Now if each pair can brighten the bulb, it's time to move on to the rectifier. Connect the AC part of the rectifier to the stator as normal, but leave the DC side unconnected. Run the bike and measure the DC output of the recitifier. It should be very high since the alternator is at full output and there is no load on the rectifier.

Thanks LOUD,

Your the man!

Peter

Ok, I did not do the continuity test because I would need to disassemble the alternator (?). It's probably irrelevant (see below)

I disconnected the rectifier and sure enough, I get exceedingly low voltage from the stator, about 13.7 VAC from any of the wires at idle and it doesn't go up much with revs, either.

Considering this test failed, I now know that "something" (probably the stator) very basic has failed inside the alternator. And apparently, when it failed it took basically EVERYTHING (rectifier, regulator) down with it. The only thing that is definitely still good on the alternator is the shaft + bearings. Considering that, this alternator is a lost cause.

So, after spending $40+ dollars on all this stuff, I'm going to just have to suck it up and pay for a new (used) alternator. I'm not bitter though, I really know my way around an alternator now.

Thanks for all the help. Hopefully this should be a lesson to all those watching this thread. MAKE SURE THE BASIC COMPONENTS (stator, field coil in this configuration) can put out good AC power (using the checks Loud Describes in his last post) before even considering the other components if your charging system is not keeping the voltage high enough.

Peter

You still need to confirm that the rotor is getting 12v to it before writing off the alternator. If it is, then there is an alternator problem. If not, then it is the regulator.

If it's the alternator, do the continuity tests.

You shouldn't have to take anything apart to do the continuity tests. For the stator, check the resistance from each of the three wires to the body of the alternator or engine. There should be no continuity. Then check wire to wire. There should be some small nominal resistance on each pair.

The "rotor" should be getting 12v because I hooked up the carbon brushes directly to 12VDC in one of my tests (made no difference) also my regulator puts out 12VDC too, so no trouble there. Whats this about the stator needing to get 12VDC? I thought that the stator OUTPUTS the AC inducted into it, unless I'm missing something

I did the continuity tests as you have said, and they came up infinite resistance (no continuity) which I assume is the correct result. 1 ohm between each stator wire.

The carbon brushes have continuity, and the rotor shaft also has the correct continuity. The field coil measures 4OHM as expected.

So it makes less and less sense to me why this might not work, but I know it's "something" in there and I'm bidding on a new alternator as we speak!

Thanks for your help.

newbikekiller wrote:

The "rotor" should be getting 12v because I hooked up the carbon brushes directly to 12VDC in one of my tests (made no difference) also my regulator puts out 12VDC too, so no trouble there..

When you did this, the rotor would have turned into a big electro magnet. Is there a way you can feel the magnetism with a screw driver or something?
I assume you put 12v to one brush and the other is somehow grounded?


newbikekiller wrote:

Whats this about the stator needing to get 12VDC? I thought that the stator OUTPUTS the AC inducted into it, unless I'm missing something

If I said that, it must have been a typo or something. I can't find the reference though.
But, you're right, the stator is the AC output device.

newbikekiller wrote:

I did the continuity tests as you have said, and they came up infinite resistance (no continuity) which I assume is the correct result. 1 ohm between each stator wire.

That sounds about right.

newbikekiller wrote:

The carbon brushes have continuity, and the rotor shaft also has the correct continuity. The field coil measures 4OHM as expected.

That sounds right too.

newbikekiller wrote:

So it makes less and less sense to me why this might not work, but I know it's "something" in there and I'm bidding on a new alternator as we speak!

Yeah, strange.
Hope the new one fixes it!