Alternator won't charge

[XSWestgate]

Hi guys,

i'm losing out on valuable riding time and am hoping to get this figured out so I can get going again. i started with misfiring and after messing with the carbs i started testing the electrical and found that the battery voltage won't increase with RPM, staying at 12.4. I made some ground today but it's not clear to me what's wrong. I'm suspecting the rec/reg is gone bad but i just installed it last year and don't want to admit that right now..

- Based off of memory and i'll double check tonight, i am getting 12.4 from the battery, 12 at the brown into regulator, and 10.5 into the +ve brush with the key on.
- Jumping the green to battery +ve while running doesn't show any voltage changes with RPM increase either though.
- stator windings seem intact with at .4-.5 ohms (.8 incl. meter)

have I screwed myself by not using the proper screws in the brush holder? I still have the stock brush holder after installing the SS Rec/Reg. Why won't i get any charge with the regulator bypass?

Thanks for the help.

Kyle

 

[Jim]

What year bike? Up thru 79 used the type B reg.... where you put 12v on the green wire for the test. 80 and up is type A where you ground the green wire for testing. What year do you have?

 

[XSWestgate]

early model, 78

 

[Jim]

Have you tried the slap test on the rotor?

 

[XSWestgate]

Yes, There’s no difference between key off vs. Key on, just a very small mag force and it’s not detected with the engine cover on.

 

[Jim]

Well, putting 12v on the green wire bypassed the regulator, so now you need to check the other brush wire and see it's grounded. Check the brushes to see they're long enough and making good contact on the slip rings. Then check rotor resistance. About 5 ohms across 'the rings and infinity to the rotor case on either ring.

 

[XSWestgate]

The brushes were fine and I just installed a new set because I had some on hand. The rotor checks out at 5 ohms but I didn’t check rings to rotor case. I’ll check those again tomorrow.

 

[XSWestgate]

Double checked some numbers:
- Voltages through regulator: 12.5 at battery, 12.1 into regulator, 10.9 to +ve brush
- Rotor is at 5.1 ohms, 5.4 with meter
- infinite resistance from rings to rotor case
- brushes seem to be making good contact.. i measured 9 ohm resistance through the brushes/rotor, is that reasonable?

now i went out to try again and i'm measuring ~13.3 volts at the battery, no charger connected, and no voltage to the +ve brush or out of the regulator.. full voltage to the regulator. now i'm concerned my meter and my regulator are pooched.

 

[2XSive]

did you do the reg/rec mod as outlined on this forum or replaced the original mechanical regulator?

 

[XSWestgate]

I can't say that i followed a mod, I bought the Solid state rectifier regulator from xs650direct (Part #24-2089 - http://www.xs650direct.com/products-30.html) and it says that it plugs directly into the stock harness and replaces the stock individual units.

 

[2XSive]

I'm sure the usual tests for solid state reg/rec applies. I assume you've read through this thread in the tech section? Scroll down and it explains how to test the solid state reg/rec. http://www.xs650.com/threads/expanded-charging-system-guide-in-progress.10561/

 

[XSWestgate]

That's right.. that's the thread i'm working off of. I've now got the bike where it will pass the slap test and i didn't really change anything other than messed with the brushes, and there may have been a poor connection there. I was excited to get it to pass that test and it seemed to run ok. Then as soon as i buttoned it back up and went for a test run, it will not fire on the left cylinder unless i have the revs high then it just fires a couple of times.. now that i've got the slap test, i'll keep going through and doing more stator testing, ignition circuit testing, and checking battery voltage with RPM tomorrow so i don't piss off the neighbours tonight. Thanks for the input so far, much appreciated.

 

[Paul Sutton]

- brushes seem to be making good contact.. i measured 9 ohm resistance through the brushes/rotor, is that reasonable?

Resistance measurements across the brushes and rotor are very unreliable. The resistance will vary all over the place, sometimes high and sometimes low.

 

[XSWestgate]

So, here’s an update. I think I’ve got the problem solved.

I was dealing with three problems:
1) I’m not good at electrical systems troubleshooting
2) I think it was the brushes that were my charging problem
3) I had a bad connection from the coil to condenser leading to no spark and confusing me because I thought my only problem was 2)
4) bonus problem that apparently the rec/reg will ground the circuit until the voltage drops below ~13.5V which threw me off on some of the slap tests.

Thanks everyone for the input, it helped me learn a lot about the bike, and here I thought I knew most of it already.

Kyle

 

[2XSive]

Glad you got it figured out. Best to go through every connection on these old bikes and clean each one, including the ignition switch assembly. A voltmeter install is a common recommendation as well. I didn't realize the reg/rec worked as you defined. Good for you to figure that out!