GL 1000 KZ: Voltage drop on the battery terminals

[Goldstein]

Hi,
The problem is a tension drop on the battery terminals of 1979 GL.When riding, once the headlight is switched on, the tension drops from 13V to 11V. As soon as I switch off the headlight, the tension comes back to 13V and more approximately. And I don’t talk about the tension that I get when idling with the head light on which is closed to 9V….
Then I started to make the battery tested by a professional retailer: the battery is in good health, despite its age of 5.
I checked the 3 yellow wire connector coming from the alternator: one spade was burnt. I cut the 3 wires, and made a direct shunt with new ones, soldered one by one, protected by a heat shrink tubing. Unfortunately,I got the same result.
I also checked the rectifier according to the workshop manual explanations. When we should have 2000 ohms between yellow and green wire, my voltmeter says 1.7 Mega ohms! When I should have to find a value between 5 and 40 ohms (I guess depending on the voltmeter ), I don’t have anything else than “infinite”. I believe that the rectifier is out of service, and this would explain the fact that it’s also very hot, even during a 5 minute idling . I own this GL for more than 34 years, and never seen that drop tension untill now. I need some advice on that electrical issue: rectifier or regulator ? Or both need to be changed ?
I believe that the alternator is in good shape: when I switch all the lights, the voltmeter can reach 14,5 V on the battery terminals, then it shouldn't be dead
Thank you in advance for your feedback, any is welcome!
Goldstein.

[WingAdmin]

I'm first going to clear up any confusion - the english word for tension is voltage.

If you disconnect the three yellow wires, run the engine at 3,000 RPM and measure the voltage (AC! not DC) across each of the pairs of yellow wires, what do you see?

[Goldstein]

Hi WingAdmin,
First of all, sorry for my "poor" English. As you probably know, French people usually don't have a very good command in the English language... You're right, "voltage" sounds better in English, and actually it will be my first learning
I'm afraid of running the engine with the 3 wires of the alternator disconnected: without any electrical load on it, the alternator might not appreciate ??

[WingAdmin]

Hi WingAdmin,
First of all, sorry for my "poor" English. As you probably know, French people usually don't have a very good command in the English language... You're right, "voltage" sounds better in English, and actually it will be my first learning
I'm afraid of running the engine with the 3 wires of the alternator disconnected: without any electrical load on it, the alternator might not appreciate ??

No apology required, your English is far better than my very poor french.

You will cause no damage running the engine with the alternator (stator) disconnected. In fact, it will put absolutely zero load on the alternator, so it will not be harmed. Keep in mind the battery will not be charging during this time. Also, be careful, as there can be dangerous levels of voltage produced by the alternator - don't touch the bare wires with your fingers while it is running.

[Goldstein]

Ok thanks for your reply.
I will make the test more "safety" now. Hope that I'll find the same AC "voltage" between the 3 pairs of wires.
I'll get back to you with the measuring result, however not before next week at the earliest .... and if everything goes well!

[Goldstein]

Hi,
I checked the voltage, first at 3000 rpm between each pairs of wires: 62 V ac, more if the rpm increases, which sounds good.
I also made a new test when the bike is cold, and obviously when the rectifier is cold. I can reach 14.5 V, and 15V on the battery terminals, as I have ever been getting for 34 years. However, the rectifier surface temperature increased very fast. It seems that when it's warm, the voltage on the battery decreased, as if the rectifier wouldn't make its job ?
I want to change the rectifier, and maybe also the regulator, especially when I see that the Honda genuine parts are not available anymore . I also saw some "old parts" on E-Bay, but I don't trust...
I found some "2 in one rectifier/regulator" which seems to be the only solution at first sight.
Do you have the same in the US, starting from the point that I would like to use a reliable part, even if it's not Honda parts ?
You might have any knowledge on the topic
Thanks so much for your advice .

[WingAdmin]

OK, so it appears your stator is good. We're left with two possibilities: One, the regulator is faulty, or two, the connector at the regulator or the rectifier is dirty. It's possible that the connector is dirty, and when things heat up, resistance increases, causing voltage drop. I would disconnect both the regulator and the rectifier, and clean the terminals with a good quality contact cleaner. If that does not solve the problem, my next step would be to replace the regulator.

[Goldstein]

Actually, I also checked the connector, and it is in good shape and no dirt on the differnt spades. However, I haven't test any cleaner on it. I might have done it, in order to be 100 % sure... you're right.
If I well understand, you would change the regulator before the rectifier in the same situation ? I found some incredible resistances through the rectifier, as I mentionned previously. On top of that, it's heating a lot ... after several minutes!
If you have to change the rectifier, or both regulator and rectifier, what would you buy in the US ?

[WingAdmin]

I can't say about the discrete units - I know the combined regulator/rectifiers heat up normally, as they shunt unused current to ground. I would expect the discrete regulator to shunt current, but I don't know why the rectifier would heat up. In any case, I would likely replace them with a combined unit.

[WingAdmin]

I missed your other question - if I were to recommend one, I would get a Shindengen MOSFET unit, you can find them here: http://roadstercycle.com/

[Goldstein]

Hi,
Back from vacation, I put a new combined rectifier/regulator ordered before leaving. I bought what seemed to be available in France (Electrosport device). I'll see if it's reliable... Anyway, I keep in memory what you suggested just in case of need
Finally, the expected voltage is back whenever the lights are switched on or off.
Thank you again for your different valuable feedbacks, I haven't got any from this "side of the Atlantic ocean"

[HawkeyeGL1200]

Not to hijack your thread.. First your English is very good. I speak only English, and am always impressed by people who can communicate in more than one language.

Second; It is very good to see you have resolved your charging system issues.

Third, and here's where the thread hijacking starts: I am very confused about the difference in these regulator/Rectifier types. Can someone (Admin perhaps) recommend a good source for me to study to better understand this better?

I do understand, or at least I think I do, how the AC is converted to DC. What I don't grasp is the differences between the two stypes that seem to be available. (R/R's I mean)

[Goldstein]

Hi,
I cannot say why two different devices can be replaced by only one ? This is clear that this 2 in 1 device seems to work fine, as it rectifies the AC into DC current and regulates the tension accordingly.
I suppose that it can do it, thanks to a "bridge diodes" . Don't ask me more, I don't remember well what I certainly learnt at school a long time ago
One thing is sure: this 2 in 1 "rectifier/regulator" makes the job of the previous separated ones: this is a "plug and play" sytem to put in the place of the previous rectifier (no need to modify the electric connector). Simply you have to disconnect and to kick out the original tension regulator.
As far as I can see on the box, it can be also used on GL 1100's.

[WingAdmin]

A rectifier changes AC (like what comes out of the stator) into DC (which is what is comes out of the battery, and is used to run the rest of the bike). However, that rectified DC voltage will have a voltage that swings wildly as engine RPM changes. We need to make sure we get a steady ~14 volts DC in order to properly charge the battery and run the bike. A regulator is what does this, using high-power transistors to adjust how much of the rectified DC is "let through" to the bike's main bus.

Because these two items are normally always together (you need both), they are commonly integrated into the same module. No real benefit of doing so other than one less item, less connectors, less space taken up, etc.

The real benefit is that transistor technology has advanced significantly in the last 40 years, so modern regulators are much more efficient and smaller than the original OEM regulators.