Should the Regulator be too Hot to Touch?

[freddy3]

Visegrippe, thanks for your input. I'll be going out to measure the rotor this evening after work.

 

[freddy3]

Here are the results of the following alternator tests:

5b: Resistance between each white wire and other white wires in the alternator connector:
~0.8 ohm.

5c: White wires from alternator connector to stator housing:
~19.7~20 ohms

6a: No breaks in brush wiring & brushes in good shape/exceed min length spec.

6b: Resistance between brush wires and green and black wires in alternate connector:
0 ohms

7: Resistance from one slip ring to the other:
~5.5 ohms
Resistance from either slip ring to the core:
∞

Bottom line: The only alternator reading that deviates from spec is 5c, which should read ∞, but I'm getting ~20 ohms between the stator housing and each of the 3 wires in the alternator connector.

So does this sound like I need a new stator?

 

[Visegrippe]

it sounds like you have a short in your stator, between the coil and the housing. that would explain the lack of charging, visually inspect it for damage and or cracked insulation.

i'm no expert but i would suspect your stator.

 

[freddy3]

Thank you, Visegrippe, that's what it looks like. But, due to the cost of the stator, if possible, I'd like to get a third opinion before I buy another one.

 

[XSLeo]

On your 72 it has a starter. The safety relay is parts of the starter system. The safety relay is actuated by voltage on the yellow wire from the alternator. The 19.7-20 ohms is the resistance in the safety relay. The yellow wire is in a single wire plug beside the large plug for the stator. Unplug the yellow wire. Retest the stator. It should read correct.
With the yellow wire hooked up the staor to white wire reading is through the relay to ground.
The book was written for the 70-71 model that didn't have a starter and no safety relay, no yellow wire. When they added the starter they didn't change the book.
Leo

 

[retiredgentleman]

As Leo said, disconnect the yellow and test again.

The rectifier is about the only thing left to test now. You can do resistance checks on it.

 

[freddy3]

On your 72 it has a starter. The safety relay is parts of the starter system. The safety relay is actuated by voltage on the yellow wire from the alternator. The 19.7-20 ohms is the resistance in the safety relay. The yellow wire is in a single wire plug beside the large plug for the stator. Unplug the yellow wire. Retest the stator. It should read correct.
With the yellow wire hooked up the staor to white wire reading is through the relay to ground.
The book was written for the 70-71 model that didn't have a starter and no safety relay, no yellow wire. When they added the starter they didn't change the book.
Leo

As Leo said, disconnect the yellow and test again.
The rectifier is about the only thing left to test now. You can do resistance checks on it.

Thanks, both of you. I can't believe the manual would get something like that wrong and I'll look for the yellow wire near the alternator plug and, presuming it's there (I don't remember seeing it), I'll retest the 3 white wires tomorrow and post new results.

Again, I've already replaced both the rectifier and regulator with NOS parts, so what's left to check?

 

[retiredgentleman]

You should do resistance checks on the rectifier, to prove that all 6 diodes are good.

 

[freddy3]

I can certainly test it, but I don't understand how the rectifier could be the problem since it's new and installing it had no effect on the hot resistor?

 

[retiredgentleman]

freddy3;

Yes, I agree, no need to test the rectifier.

After reviewing the thread I still believe your problem is with an intermittant short in the rotor, as I mentioned in post #23. The fact that you saw battery voltage swinging from 13.5 to 15.75 tells the story. The rotor is shorting out and batt voltage drops; the short then disappears and the battery voltage swings very high to 15.75 volts. The regulator can't handle that kind of rapid swing,and overshoots to the 15.75 volts.

The resistor in the regulator is 8 ohms and normally only dissapates about 9.6 watts, when battery voltage is around 14.2 volts. During the cycle swings, with the voltage greater than 15 volts, the resistor current increases to about 1.9 amps and wattage to 29 watts, which is hot! The regulator uses the resistor as a load to try to reduce alternator voltage.

So, even though your test of the rotor seemed to be normal with the engine off; when the engine runs, the vibration must be causing the short to appear.

You need to get a new or rewound rotor and all will be well.

I can't agree with your manual that says 14.5 to 15 volts. That will tend to cause water loss from the battery. Below 14.5 is better, with 14.1 or 14.2 just about perfect.

 

[freddy3]

retiredgentleman, thank you. That makes complete sense. And, coupled with the fact that I had to replace the rotor 4 years ago for what I vaguely recall was a similar problem, I'll order another rotor today from mikesxs.com.

As far as the 14.5-15 volts goes, I'm not sure what to make of that since it came from the official Yamaha Service Manual (part LIT 11613-0601).
I'll report back with the (hopefully optimistic) final results after I get the rotor installed.
Many thanks for your (and others' help).

 

[XSLeo]

In the factory book that voltage is with the fuse disconnected.The meter hooked to the regulator side of the fuse box. This will be charge voltage with out any load, so it might be a bit higher.
The only problem I have had trying to do the test that way was the bike quits when you unhook the fuse.
You have both a regulator and rectifier replacements and it acts the same with both or either replaced. It might be the rotor, it might be a weak, intermittent ground. I might check grounds before spending money on a new part.
If I was to replace the rotor, a rewind is better than Mike's new rotors and about $100 less. Call Gary at Custom Rewinds, 1-800-798-7282. $125 last time I checked.
Leo

 

[freddy3]

Thanks for that info, Leo. I've written down Custom Rewinds info for future reference. Unfortunately, your post came a few days too late as I ordered the rotor (from Mikesxs) a few days ago & it should be here by Tuesday.

I'm pretty certain that whatever's currently causing the regulator resistors (both on the original regulator & NOS regulator) to heat up happened as a result of a specific event like the rectifier shorting out. I have three reasons for this: 1) Something similar happened four years ago and, if memory serves correctly, replacing the rectifier & rotor did the trick; 2) the incident four years ago occurred a day after I'd washed the bike, as was the case this time; and 3) in this case, the day after I washed the bike, the battery terminals, rectifier and battery fuse all became blazing hot right after I'd started the bike (I should mention that I also replaced the battery fuse, holder and wiring when I replaced the rectifier & regulator). Remembering what'd happened four years ago, I knew to check the rectifier for corrosion and possible shorting within it, which is exactly what I found. After disassembling and giving it a good clean with brake cleaner (so all of the corrosion/shorts were removed) and then thoroughly drying it, all the components that were getting hot went back to normal temp (except the regulator resistor, which I only became aware of during my final inspection before putting all the covers back on).

So, all in all, I don't think the hot resistor's the result of a bad ground in wiring. It's pretty much gotta be a short within one of the charging components and the rotor seems to be the part that I believe solved the similar problem four years ago.
If that doesn't solve the problem, I do have a NOS wiring harness I could install as a last resort, but I just don't see how that could be the problem since the wiring doesn't appear to have any insulation missing, nor had any of the wires been disturbed prior to the original battery/rectifier/fuse becoming hot.
In any case, sorry for the lengthy diatribe. I appreciate your input.

 

[plane_ben]

Take it from someone whos' been there with normal looking wire. I play with VW buses as a hobby also, and I've seen many a normal looking wire be corroded deep into the insulation. As you seem to wash your bike alot, I wouldn't be surprised if quite a bit of you harness is corroded. I'd replace your harness if I was in your position.

 

[freddy3]

I guess that'll be the next step if the rotor doesn't solve the problem.
Thanks, Ben.

 

[freddy3]

Well, it's not the rotor.
I just installed the rebuilt rotor from Mikesxs, but it had no effect on the hot resistor.

Before I go through the trouble of replacing the entire wiring harness (which I'm still not convinced is the problem), I'd like to eliminate any other possible causes. For one, there's a relay just below the regulator and I've got a NOS replacement, but I was too hot/worn out after the rotor to replace it. Is this relay related to the charging circuit and could it possibly be the cause of the hot resistor problem:

Also, does it seem reasonable that, if in fact the old rotor was causing the problem, that it could've damaged the just-replaced NOS regulator and rectifier? That is, could I be chasing my tail here?

Should I re-look at the stator?

Anything else?

 

[freddy3]

I guess I've stumped the audience.

Anyroads, today, armed with the Yamaha Service Manual, my DVM and an analogue volt/ohm meter (used as a double-check on my DVM readings), both of which have been fitted with fresh batteries and adjusted, I went back and retested.

First, I installed the NOS relay indicated in the previous post. Then, I disconnected all of the components related to the charging circuit from the wiring harness, including the black rectifier ground lead that runs through the harness and terminates at one of the two ignition coil bolts. I tested every section of the harness for physical/electrical breaks and/or shorts, but found neither. The wiring harness seems to be okay.

Then, I reconnected all of the charging components to the wiring harness and started the engine to see if I might've inadvertently remedied a loose or poor connection previously overlooked. But the regulator resistor still heated-up within 30 seconds.

Next, I went through the charging circuit resistance diagnostics in the Service Manual from beginning-to-end, double-checking all of my DVM readings with the analogue meter. They matched. However, this time, both the stator and the (just replaced) NOS rectifier tested faulty.

In the case of the rectifier, it failed tests 4 & 5 - I'm getting infinite resistance in both directions.
However, based on a previous post citing errors in the Yamaha manual's diagnostic specs, I decided to do some separate diode tests not indicated by Yamaha. Oddly, both the NOS rectifier I just installed the other day & the one it replaced checked out fine in the diode tests. Not sure what to make of that since both rectifiers fail the resistance tests in the Yamaha Service Manual:

In the case of the stator, instead of infinite resistance when testing between each of the three white wires in its connector and the stator housing, I'm getting essentially 0 resistance (i.e., a short), which I think retiredgentleman suggested as a possibility early on. So, I ordered a NOS stator and another NOS rectifier and will repeat the tests on both components prior to installing them on the bike. I'll also retest after I install them, but before starting the engine. Since all of the other charging components passed the tests, hopefully, that'll do the trick.

 

[retiredgentleman]

freddy3;

For diode testing, the Yamaha manual is not correct. Its normal to measure 6 or 7 ohms in one direction and infinity in the other direction.

Now for the stator; back in post #42, you measured 20 ohms from whites to stator frame. XSLeo and myself both said you needed to unplug the yellow wire, in order to measure the stator resistance to ground. That's because the 20 ohms is the relay coil of the safety relay. You never got back to us if you found the yellow wire and unplugged it.

That extra relay you have pictures of, has a yellow wire, which I suspect is your safety relay. That yellow would have to be disconnected, in order to test the stator.

Now you say the stator measured 0 ohms. Did you measure this with the yellow wire disconnected? Did you use the lowest ohms scale, usually 200 ohms?

 

[freddy3]

For diode testing, the Yamaha manual is not correct. Its normal to measure 6 or 7 ohms in one direction and infinity in the other direction.

I'm not even getting that 6-7 ohms (on either rectifier).
I have three manuals (the OEM from Yamaha (which contains all their Technical Bulletins and Updates through 1975), a 1982 Clymer and the current Clymer), and they all repeat the same specs (though the Clymers obviously re-wrote the text) without any correction for the diode tests. Strange.

Now for the stator; back in post #42, you measured 20 ohms from whites to stator frame. XSLeo and myself both said you needed to unplug the yellow wire, in order to measure the stator resistance to ground. That's because the 20 ohms is the relay coil of the safety relay. You never got back to us if you found the yellow wire and unplugged it.
That extra relay you have pictures of, has a yellow wire, which I suspect is your safety relay. That yellow would have to be disconnected, in order to test the stator.
Now you say the stator measured 0 ohms. Did you measure this with the yellow wire disconnected? Did you use the lowest ohms scale, usually 200 ohms?

I'm sorry, but between the heat, the travel (I store the bike in a 6'x8' unit at a public storage and have to work on it in the parking lot) and the various tests, I completely forgot about that yellow wire. But I think you're right about it being the one coming out of the relay's wiring bundle (that's the only yellow wire I saw when I checked the wiring harness), so I'll try to recheck the rectifier (with the yellow wire disconnected!) tonight and report back here.

In any case, both the (new) NOS rectifier and stator are already en route and if it's not either (or both) of those components that're causing the hot resistor, I don't know what else to test? There's literally nothing left on the bike that's related to the charging circuit that hasn't either been replaced (some more than once!) or repeatedly tested.

 

[freddy3]

Now for the stator; back in post #42, you measured 20 ohms from whites to stator frame. XSLeo and myself both said you needed to unplug the yellow wire, in order to measure the stator resistance to ground. That's because the 20 ohms is the relay coil of the safety relay. You never got back to us if you found the yellow wire and unplugged it.
That extra relay you have pictures of, has a yellow wire, which I suspect is your safety relay. That yellow would have to be disconnected, in order to test the stator.
Now you say the stator measured 0 ohms. Did you measure this with the yellow wire disconnected? Did you use the lowest ohms scale, usually 200 ohms?

Unfortunately, you were correct about that yellow wire. With the yellow wire (coming from the relay harness) disconnected, I'm getting the correct readings on the stator (i.e., ~.8ohms between each of the white wires & infinite resistance between the stator housing and each of the white wires in the stator connector).

I say unfortunately, because, unless I've missed another recommendation in this thread or the 2nd NOS rectifier (which arrives tomorrow) remedies the hot regulator resistor problem, I'm out of charging components to replace or check...