Topic: Alternator testing

[El Taco]

I've done all the tests in my manual, but I figure with it being an alternator, it should put out some voltage that I can read with my meter. Which wires should I check while it's running to see what it's putting out? I get nothing on each one, so I figured I'd check it with the ground in the plug but to no avail.

[El Taco]

Forgot to add it's a 75 CB500.

[the_genrl]

frame is ground.  you have 3 yellow wires from stator, making power like the 220v 3 phase in your house, but less voltage .  put your meter on ac and read one yellow wire at a time and the other meter lead to ground.  that should give you voltage values for each stator winding.

this is your first step.

[oldbiker]

The correct way is to measure between any two yellow wires from the alternator. Thus there are three readings to be taken. These will be an alternating voltage and can be up to about 50 volts ac. It is the rectifier and regulator which control it down to the 13-14 volts dc to charge the battery. The three readings you take should be approximately equal. If they are not then it suggests that one winding of the alternator has a break in it. Also use the faultfinding chart from www.electrusa.

[n9viw]

The site Oldbiker just referenced is http://www.electrexusa.com ... more specifically, http://www.electrexusa.com/electrex_fault_finding.html . Download that .PDF and print it out, and follow it TO THE T! I was sure my alternator was at fault (since it was the oldest part of the electrics, and never replaced) but it turns out the regulator on my brand new Electrex RR24 is fubar.
Oldbiker is correct in that AC voltage should be measured between pairs of yellow wires, but the voltage range can be anywhere from 15-20VAC at idle to 80-85VAC at a hard rev. Ideal is 50VAC at 5k RPM, that ensures there's enough voltage for the reg and rectifier to work with to charge the battery.
If you don't already have a Honda factory service manual, get one. They can be downloaded in .PDF format in sections from http://www.honda4fun.com/man_officina/man_officina.html . Download your model, print it out, three-hole punch it, and put it in a binder to keep in the shop where you work on your bike. NOTHING, not Clymer, Chilton's, or even Haynes (my personal favorite) can compare to the FSM.

[El Taco]

Done all of the above, except I haven't  checked out the links yet. I didn't think to check for AC. I'm used to internally regulated alternators on cars. I checked it for AC between the frame and the yellow wires, then from wire to wire.

Still nothing.

Let me bolt up another alternator and see what happens.

[El Taco]

Okay, so I bolted another one on. I get a  0.01 with my meter set to 200VAC between the yellow wires, and nothing grounding to the frame.

[El Taco]

Okay, 3rd one I bolted up gives me a reading of about 0.09 at the most. That's revved at about 5k. I have only two AC settings on my meter, 750, and 200, so I'm on 200. I only get that reading between the yellow wires, and not to the frame.

[Warlock]

Greets,
Here is something to consider. When measuring AC voltage on the legs of the stator, it is assumed that full field voltage is being applied. The AC output of the stator is directly related to the field current. If field current is not at maximum, AC voltage will be determined only by the field current being supplied to the field coil(if any). To eliminate the effects of high resistances or opens in the harness, apply 12v directly to the field coil leads when testing. Even at low RPM the alternator output should be at maximum due to full field current (full load is sometimes sufficient to stall the engine...). Perform this test just long enough to obtain the voltage readings as full field and open output can generate a GREAT amount of heat in a short time. If the readings are within reason performing this test, I would suspect regulator/rectifier wiring harness issues limiting field current. Happy hunting...

Ride On....

[mcpuffett]

when i test for voltage coming out of an alternator be it bike or car i connect onto battery with motor running and take reading that way at different rpm's   mick.

[Tim2005]

I'm with Warlock on this one... the centre of the alternator is basically an electromagnet, it should be a fairly powerful one too when tested on the bench with 12v applied. If it has failed, or is not getting current or a good earth, then the alternator won't produce anything. Also, in line with mcpuffet's post, testing at the battery is my usual check, but I'd also add that to get these charging systems to work you do need a battery that is in decent condition to start with.

One other idea, assuming the 500 is the same as the 400, check the wires where they join the rectifier, one (red I think) has a habit of corroding through & breaking off, cutting off all charging.

[n9viw]

I'm starting to think these 500/550 stators and field coils are naught but garbage. In spite of the fact that mine measure well outside acceptable ranges, I've been told that they should work fine. I tested mine yesterday manually full-fielded with the rectifier disconnected, and got 40-85 VAC at each of the pairs on the stator.
Tonight I tested a stock reg on a power supply (shunted at 14.5v) and a rectifier from Rick's Motorsports (proper diode readings, no shorts). I connected them to the alternator, started the bike, and barely got up to 12v DC at the battery even at an insane rev.
I'm bidding on another 550 alternator on ebay right now, and am hoping that does the trick. If not, after rewiring three times, two regulators, and a new rectifier, I have no idea what's left to do.

[the_genrl]

reading the manual, yes the stator has in isolated ground so i was wrong that the stator ground is apart of the frame gound.  like a car, AFTER the power is rectified, then it is gounded. 

if you measure from yellow wire to any yellow wire, you should get aprox. rms values of the two wires you are measuring.  pretty useless numbers, unless you want to figure them out.   

id say your best bet would be to check to see if the rectifier diodes work, then if so, connect the 3 wires and measure the voltage from - to +.

[the_genrl]

I'm starting to think these 500/550 stators and field coils are naught but garbage. In spite of the fact that mine measure well outside acceptable ranges, I've been told that they should work fine. I tested mine yesterday manually full-fielded with the rectifier disconnected, and got 40-85 VAC at each of the pairs on the stator.
Tonight I tested a stock reg on a power supply (shunted at 14.5v) and a rectifier from Rick's Motorsports (proper diode readings, no shorts). I connected them to the alternator, started the bike, and barely got up to 12v DC at the battery even at an insane rev.
I'm bidding on another 550 alternator on ebay right now, and am hoping that does the trick. If not, after rewiring three times, two regulators, and a new rectifier, I have no idea what's left to do.

sounds like there are lots of cases of electrical problems with these bikes.  what happens exactly?  do you all of the sudden see it cut or does the voltage just get less and less everyday?   when you take the stator off, do you see a spot where the wire opened?  or when they go bad, does the voltage just get less and less everyday? 

if the voltage stops working right away, i would guess a blow somewhere in the stator lines or a blow in something.  but if it just trickles off to a lower value gradualy there might be something to the magnets in the rotor (gradualy looseing emi).  dont have any idea how you could figure that, unless you had a brand new one and compared them.

as for the loading the stator with 12v to see if it becomes an electomagent, you can but make sure you put a resistor somewhere in there!  i bet the stator line (20 guagish? not sure about cb500s) can handle about 7 amps tops before its starts getting ugly.  assuming you have tested a low resistance between the field coils, apply an amp or so to see if it has any effect on metal  (1 amp = 12volts / 12ohm resistor.) 

[n9viw]

sounds like there are lots of cases of electrical problems with these bikes.  what happens exactly?  do you all of the sudden see it cut or does the voltage just get less and less everyday?   when you take the stator off, do you see a spot where the wire opened?  or when they go bad, does the voltage just get less and less everyday? 

I don't know about others, but mine has been up and down- Some days it would charge, some days it wouldn't, so I'd get a week or so on a charged battery, but by Friday if I hadn't recharged the battery I'd be stranded. This last time, I got ONE ride in, and then the battery started going.

if the voltage stops working right away, i would guess a blow somewhere in the stator lines or a blow in something.  but if it just trickles off to a lower value gradualy there might be something to the magnets in the rotor (gradualy looseing emi).  dont have any idea how you could figure that, unless you had a brand new one and compared them.

Well, there's the rub- there ARE no brand new ones. I have not found a single manufacturer of new stators or field coils for the 550. You may be able to get them rewound, but those services are few and far between anymore. I'm thinking of trying to learn how to do it myself.
And you would think that if the voltage dropped out immediately, you had a blow in the line, but sometimes a weak spot just gets hot and adds resistance, or might short two windings together and LOSE resistance. You never really know.

as for the loading the stator with 12v to see if it becomes an electomagent, you can but make sure you put a resistor somewhere in there!  i bet the stator line (20 guagish? not sure about cb500s) can handle about 7 amps tops before its starts getting ugly.  assuming you have tested a low resistance between the field coils, apply an amp or so to see if it has any effect on metal  (1 amp = 12volts / 12ohm resistor.) 

Personally, I wouldn't put 12v INTO the stator, because it's made to put power OUT. The resistance on the stator coils is only .35 ohms. If you put 12v into a .35 ohm load, you have the capacity for almost 35 amps of current! Not a good scene. On the other hand, putting 12v into the 5 ohm load of the field coil is only 2.4 amps, so it's made to take it. Resistance is really the only safe way to statically test these parts.

[bryanj]

Sorry but in 35 years i have NEVER seen an electrical duff 500 generator!!(ONLY Physically damaged) ALL the problems are bad grounds/ bad connections or badly adjusted regulators