No output from alternator


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XJSRider
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No output from alternator

Post by XJSRider »



So this one was my fault, and I thought I figured it out a couple times, but no luck. I had removed the alternator while working on clutch slave and a brake line hose back there.

I have always checked alternators in the past by putting a voltmeter to the battery when it was running. When car/bike is off you get 12.5-12.8v, then turn car/bike on, test battery voltage again, maybe giving it a little gas and you should see between 14-15v.

I have no change in voltage. I've checked at the battery and at the big wire going into alternator.

Big wire disconnected from alternator, test wire to ground, get battery voltage.

The small wire in the back... battery voltage when key is on.

I did do a pretty good screw up, I started taking that big wire off before disconnecting the battery, and my wrench hit the frame and caused an arc. Vaporized the dog bone fuse next to the battery. Could this have nuked the regulator? It worked before I broke it :)

Battery is a little low, 12.1 volts. But it should still show 14+ when running, correct?

Any ideas what to check next? This site has been a life saver.



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DenverWinger
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Re: No output from alternator

Post by DenverWinger »

Possible that sparking killed the regulator.

You can take the alternator to your local automotive alternator/starter rebuilder shop. They should be able to both test the regulator and find another for not very much $ if yours is toast. It's basically an automotive alternator with a custom "nose" on it for the 'Wing engine.
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Re: No output from alternator

Post by CrystalPistol »

That big dog bone fuse that was under the cover right beside the battery is Main Fuse "B", 55 amp.

You know there is another Main Fuse "A" located in the top of relay A don't you? It's 30 amp. It is not a dog bone. Relay "A" is in there behind the dog bone fuse holder you spoke of.
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XJSRider
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Re: No output from alternator

Post by XJSRider »

Hi CP. Yes the 55 amp is what blew, the 30 is good.

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XJSRider
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Re: No output from alternator

Post by XJSRider »

I ordered a db electrical high output to replace the one I think I fried. 100 bucks shipped wonder how long it will last. I don't understand why people say these fail so much I would think that we would have figured out how to build one by now.

I have some questions maybe people can chime in:

1. I want to fix my old one to have a spare and learn more about them. Is a regulator and rectifier the same thing on these alts? From partzilla it is like 200 bucks but for what it is it should be way cheaper. Ken has for 25 bucks which seems much more reasonable. But he seems a bit grumpy can't get a straight answer from him is regulator/rectifier the same thing, that little box that sits on the back of the alt with the exciter wire connected to it.

2. Double the 55amp dogbone fuse with high output. This doesn't feel right. The bike was running fine with stock alt. I have a bunch of extra non-led lights on this thing and some USB chargers, maybe will add some heated gear plugs down the road. But I am pretty sure I am under 40 amps all in. The thought for going high output was it would not need to work as hard and should last longer. Doubling the fuse seems like you could put the wiring harness in harm's way. Just because the unit is rated for 85 amps doesn't mean it is spitting out 85, it should only be pushing what is needed, so the 55amp fuse should be plenty.

3. 85 amp will boil your standard battery. Like above... if battery was fine before switching to high output alternator, I have a hard time believing it will cook the battery. The alt should be putting out no more juice than the last one, otherwise the regulator/rectifier is not working, correct?

Thanks.

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AZgl1800
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Re: No output from alternator

Post by AZgl1800 »

Need to correct some thinking here:

the Amperage capability of an Alternator does NOT effect the condition of the battery, in the sense that a 200 amp Alternator would cook a small battery like for our motorcycles. It will NOT !!!!

Most alternators have Internal Regulators, that sense Voltage, and when the battery voltage rises to 14.4 they stop pushing current past that point. Some Alternator's have Temperature Sensing Capabilities.... these use a sensor that is "glued to the battery case" and the Regulator will reduce the charging voltage when the battery gets too warm from being over-charged. I wish all of our bikes were set up that way, it would greatly increase the life of our bike batteries....

they are killed prematurely from over charging and from being allowed to drop in voltage between rides.... this is where a Battery Tender is of tremendous benefit... ( my bike always has a battery tender plugged in )

as the temperature of the Alternator rises ( due to engine heat ) the Regulator circuit gradually reduces the "regulating voltage" until it normalizes at 13.6 volts when every thing is hot and the battery is fully charged.

So, replacing a 40 amp Alternator with a "high output" alternator will ONLY give you the ability to ADD MORE LIGHTS, it does NOT increase the ability to charge the battery beyond what it needs.

.
~John

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ct1500
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Re: No output from alternator

Post by ct1500 »

XJSRider wrote:
Tue Sep 08, 2020 10:47 am
1. I want to fix my old one to have a spare and learn more about them. Is a regulator and rectifier the same thing on these alts? From partzilla it is like 200 bucks but for what it is it should be way cheaper. Ken has for 25 bucks which seems much more reasonable. But he seems a bit grumpy can't get a straight answer from him is regulator/rectifier the same thing, that little box that sits on the back of the alt with the exciter wire connected to it.
A voltage regulator has a set point of typically 14V+/- and will keep this constant voltage state on the charging system by applying voltage to the field coil (rotor via the brushes) which in turn cranks out more amperage when needed as load devices are switched on. As load devices are turned off a voltage regulator will sense an increase in charging system voltage and reduces field coil voltage thus reducing amperage output which all happens in milliseconds.
Your alternator is producing AC voltage and the job of the rectifier plate which contains the diodes is to convert it to DC voltage. The voltage regulator is the small black box which house the brushes and output sensing electronics, the rest of the assembly is the rectifier plate. The R/R assembly will usually be supplied as one piece as they get fitted together by soldering but can be ordered individually which is more labor intensive. The stator also gets soldered to the rectifier. If when inside a component doing a repair good shop practice dictates replace all for a more positive outcome.

XJSRider wrote:
Tue Sep 08, 2020 10:47 am
2. Double the 55amp dogbone fuse with high output. This doesn't feel right. The bike was running fine with stock alt. I have a bunch of extra non-led lights on this thing and some USB chargers, maybe will add some heated gear plugs down the road. But I am pretty sure I am under 40 amps all in. The thought for going high output was it would not need to work as hard and should last longer. Doubling the fuse seems like you could put the wiring harness in harm's way. Just because the unit is rated for 85 amps doesn't mean it is spitting out 85, it should only be pushing what is needed, so the 55amp fuse should be plenty.
An alternator will only output the amperage required to satisfy the 14V+/- set point of the voltage regulator and when the alternator cannot output the amperage needed it is full fielding and tapped out, charging system voltages drop from this set point. Same goes for your home AC backup generators, when a big load gets turned on amperage requirements go up field coil voltage increases and the engine grunts and groans with the governor opening the throttle to produce amperage. The 1800 GW has about an 80A alternator and the main fuse is somewhere around 110-120A. :)
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Re: No output from alternator

Post by MikeB »

XJSRider wrote:
Tue Sep 08, 2020 10:47 am
...
that little box that sits on the back of the alt with the exciter wire connected to it.
That little black box on the rear of the OEM alternator is simply a noise filter. It is there to help shunt alternator electronic noise to ground.
MikeB
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USAF Avionics Communications Tech - 1968 - 1986 / Flight Engineer C-130E - C-141B - 1986 - 1992. Retired
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Retired in Tacoma, WA

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XJSRider
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Re: No output from alternator

Post by XJSRider »

Thanks for all the awesome responses!!

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Re: No output from alternator

Post by Solo So Long »

AZgl1800 wrote:
Tue Sep 08, 2020 11:01 am
Need to correct some thinking here:

the Amperage capability of an Alternator does NOT effect the condition of the battery, in the sense that a 200 amp Alternator would cook a small battery like for our motorcycles. It will NOT !!!!
. . .assuming that it is putting out the proper voltage. A shorted diode can ruin a battery. Rapidly.

When there is an electrical problem, don't just "check voltage," check both DC and AC voltage. AC voltage should be 0.



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