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1980 CX500D
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Discussion Starter · #1 ·
Hey everyone! I am have a charging problem, and I luckily have a parts bike that's had a lot of parts I've needed but I ran out of luck here. I've tested both stators and both rectifiers, and I have 2 good stators and 2 bad rectifiers.. so I went the cheap option and found a $25 one on Amazon and it came out of the box failing, and it was wired wrong.. my cx500 is stock and I wanted to know what has been a good option for you guys so I can get this thing back on the road. Thank you in advance!
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Discussion Starter · #3 ·
So I did a continuity test on the stators and rectifiers. And my rectifiers aren't giving me any resistance and I have a new battery. But I'm not exactly knowledged so if there is anything else I can test or check or that I missed please let me know.
 

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'84 CX650E that is evolving into a GL500
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What do you mean by "my rectifiers aren't giving me any resistance"?
These bikes (& many others) have 3 phase alternators (an alternator is an AC generator)(Do you understand the difference between AC and DC?) so the rectifiers consist of an array of 6 diodes (a diode is a component that allows current to flow in one direction but not the other).

In the days when analogue meters were all there was we tested diodes by measuring the resistance in each direction, expecting to see high resistance one way and low the other.
These days most meters are digital and include a diode test function that tells you what the voltage drop across the diode is. Instead of looking for high resistance one way and low the other you should see something between 0.5 and 1V in one direction and no reading in the other.

What made you suspect that the rectifier was the problem? Did you measure the voltage across the battery at 2500 RPM or higher?
 

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Discussion Starter · #5 ·
I get no resistance at all in any direction across any wires. And I have a brand new battery and my RPM gauge currently doesn't work. It's on my list of things to fix but its not that important to me.
 

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I don’t think you are understanding what a regulator/rectifier does or how to test it. You keep telling us you have a new battery, which is great, but has nothing to do with whether your rectifier is functioning properly. I am just guessing here, but I don’t think the rectifier is your problem. I would first, learn how to test the charging components and then test everything again.
 

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I watched a few videos of other people also testing their charging systems and followed those steps.
Not all you tube videos are accurate. Anyone can post a how to video and not know their head from their you know what. You should follow testing advice given here on the forum and follow the Factory Service Manual.
 

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Discussion Starter · #10 ·
Agreed, which is why I have watched a good hand full of multiple people on my model bike. And thank you for the link but that leaves right where I am.
 

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One way to fix a problem is to start replacing parts until the problem is fixed, the other is to do a proper diagnosis and then only replace the parts needed. Have you downloaded a copy of the factory service manual for your bike? Find on in the wiki, link in my signature. Good luck!
 

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Are you sure you are using the meter correctly? What scale do you have it set to? What does it read when the leads are touching and when they aren't touching?
 

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Discussion Starter · #13 ·
I am using the correct setting, mine sounds a little alarm and gives a reading when there is a completed circuit to measure resistance. So when my leads are not touching it reads 0. When they touch they sound an alarm and settle on 0.something I didn't take a picture.
 

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OK, that's right. Now does your meter have a diode test setting?

I'll ask again:
What made you suspect that the rectifier was the problem? Did you measure the voltage across the battery at 2500 RPM or higher?

And did the videos you watched cover testing the charging portion of the stator or just the CDI portion (which is completely separate)?
 

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Discussion Starter · #15 ·
The videos I watched covered testing the stator and testing the regulator. I don't have an RPM gauge, so I have not tested my battery. What will testing my battery tell me.
 

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We aren't telling you to test your battery, we are telling you to test the charging system and there is no point in trying to fix a problem if you haven't figured out what the problem is.

A charging system works by presenting a voltage to the battery that is slightly higher than the battery's voltage so that current will flow into the battery.
The output of the alternator depends on how fast the engine is turning and for charging systems like on these bikes that means that there isn't enough power to run the lights and charge the battery while the engine is idling but by the time you are moving fast enough for the engine to turn at about 2500 RPM the alternator is making enough power that the voltage measured at the battery should be between 14 and 15V (the voltage regulator prevents the charging system voltage from getting any higher than that no matter how fast the engine turns).

Knowing the exact engine RPM is not critical for testing the charging system. If your tachometer isn't working rev the engine to something that sounds about like it does while riding in 5th gear at about 30 or 40 MPH while measuring the voltage (someone please confirm that that is about right - I don't pay that much attention to the tach).
If the charging system is producing between 14 and 15V your charging system is working. If the voltage is more than 15V the regulator part of your regulator/rectifier is not working correctly and if it is is less than 14V there is something wrong with either the stator, the rectifier part of the regulator/rectifier or the connections between them.

BTW: The most important part of the tachometers on the CX/GL500/650 family of bikes is the temperature gauge. We've had a few reports of engines that might not have been ruined if their owners had known that they were overheating sooner.
 

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Discussion Starter · #17 ·
Well when I take my bike for a 40 minute ride and turn it off, and then go to ride back home and it's dead, I have a charging problem. I've taken multiple trips and its not charging. That's why I started testing the charging system. I didn't test it at the battery feeling pretty confident there isn't any power making it back to it.
 

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Well when I take my bike for a 40 minute ride and turn it off, and then go to ride back home and it's dead, I have a charging problem. I've taken multiple trips and its not charging. That's why I started testing the charging system. I didn't test it at the battery feeling pretty confident there isn't any power making it back to it.
Your test of the stator revealed that it was generating electricity properly?
 

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Measuring the voltage at the battery is the first step in testing the charging system.

Just a thought: How long is the bike parked between riding it and not being able to start it? If it is just a few minutes maybe the charging system isn't working but if it is several hours it is possible that it is charging OK and something is causing it to discharge while parked.
 

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Discussion Starter · #20 ·
My test of the stator indicated no breaks to ground and I have continuity on all three leads. I turn my bike off for not even 5 minutes and it's dead. Nothing draining the battery, it's just not charging.
 
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