Alternator/Generator

Hi all, greetings from across the pond

New to the site and not had to post much as so much good info available.

However, during my XJ750 project I recently discovered that my alternator is only putting out 11.94V when measured accross battery terminals. Using the haynes manual and this site I have checked alternator brushes and these are all in spec. I then proceeded to check the windings on the stator for resistance and now am stumped and scratching my head!

Not sure what an Ohms x 1 scale is? so I set digital multimeter to lowest Ohms setting 200 on my meter. Readings for each of the three tests provide similar 0.6 0.7 0.7 readings is this right - normal ?

Haynes indicates I should get readings of 3.6 - 4.4 am I reading these figures on a different scale?

Or is my altenator /generator broke?

all help and advice would be gratefully received. Once I have eliminated this element I will progress onto checking regulator/ rectifier.

Many thanks in advance.

 

The field resistance resistance is the colored wires the haynes 3.6 to 4.4( I dont have specs handy) For the stator the white wires it should be a low number 0.?? ohms . When taking resistance readings dont let your fingers touch the probes it will include your body resistance in the Number you get, also unplug from the wire harness / component or the reading will be way off.

 

In regard to the brushes: Examine the little braided lead wires carefully, make sure they're not all green and corroded on the inside while appearing fine on the outside. The corrosion can "hide."

 

Also as I found out, polish the rings of the rotor so they're nice and shiny -- I thought mine were ok, but I was getting low output as well. After the bike left me stranded with a dead battery, I was pretty sure either it failed, or the regulator failed.
Turns out polishing those rings made all the difference in the world. Charges like a champ now.
I took some 220 grit finishing paper to clean any corrosion off, then used some metal polish on a dremel polishing bob until they were near mirror smooth.

 

Thanks for all advice, I have read your write up Altus and had polished rings on rotor.

It also pays to re-read haynes manual stator readings from white wires are 0.41 - 0.51 - Mine are obviously better thanks Waldo you made me recheck.

finally thanks Bigfitz when I reasemble alternator I will check lead wires.
Hopefully reasemble next weekend, I can then check on remaining electrics or statr testing regulator / rectifier.

 

If you are testing the voltage at the battery, remember the juice is passing through the reg/rec.

 

Welcome to the site CapnRedbeard.
The system won't charge at idle.
Hook up your volt meter once again, start the bike, watch the meter and rev the engine up to 2500 rpm. The voltage should increase!

 

i beleive that close to zero readings should be observed between connections. on the lowest ohm setting. your 3 white wires. a broken connection would show something other then zero.

the next test is to probe one of each of the 3 white wires to ground and you should have NO reading on the lowest scale. any reading indicates that winding is grounding out. generally due to broken insulation of the winding.

according to a delco-remy class i once took. that's pretty much standard testing for any type of alternator/generator.

the easiest test for votage output is to watch the headlight. as stated above. the bike runs on battery at idle. rev the motor and charging increases. which means the headlights will also grow brighter.

rev the throttle and see if the headlight gets brighter. but don't wrap the motor. no need to full throttle. a voltmeter will give you exact readings.

 

Ok, to update all systems are go..

Polished rings, cleaned brushes, checked and cleaned everything. reasembled and still not charging properly.

Traced wiring to regulator 8 way connector and noticed green gunge around the red wire. not to much but when I split the connector the spade connector came away in female half. As a temporary measure seperated cables sliced them together and now all systems working fine.

thanks to everyone for assistance, as this bike has not been run for approx 12 years I anticipate a few more problems, however thanks to rhe site were up and running. Roll on the summer.

 

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Wow, great advice!

 

How does one go about flagging spam for removal?

 

WE need someone who has the authority to just kill these spam postings.

 

Killing spam is within the power of the Moderators. Send them a PM when you see it, and don't click on any of their links (if they track clicks, or views, then it'll just encourage them).

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