charging at idle

offthewall

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79 SF with PMA, Pamco. Im running all incandescent bulbs in my signals/running, brake/running, and headlight. Im wondering what I should be getting for voltage at idle around 1200 rpm. With no lights on i get 12.4v-13v. With all lights on I get down to 11v-11.5v. Essentially with the headlight on, I can't get above 12v at idle which I see as a problem.

Battery is brand new
reg checks out
fuses check out
:wtf:
 
LOL IAC I can guess.......

Yamaha spec'd 1200 RPM as idle speed to get the stock alternator up to charging speed as much as any other consideration.
What headlight? Some H4 auto bulbs are higher wattage than the typical MC alternator can handle at low speed. Some after market headlights have a "city bulb" in addition to the headlight bulb that draws much less current. keeps the shell lit but reduces draw. Don't know what parts you have, alternators are fussy about alignment of rotor and stator to get the best output.

We just had an 81 in the shop with "low charging issues", after a full check out of the charging system we found the "brand new aftermarket" VR was weak, I didn't do a diode test but suspect it had a bad diode.

This old 650 rider thread lists some good VR choices.
http://www.650rider.com/index.php?name=Forums&file=viewtopic&t=5811

Any fault that knocks one leg out of a three leg alternator will present as "low charging". So measure and check first ohms then running AC voltage output on the 3 white wires. Not sure of the PMA specs but 20 volts or so AC would be a guess.
 
Thanks Gary I'll have a Harley headlight with an auto bulb in it. I'll double check the wattage. My output doesn't seem to be an issue I get upwards of 14v as rpms increase. I'll also double check alternator output. Like I said, the reg/reg checks out. It's from xs charge and all diodes are good.
 
If you're using a 55 watt headlight, you could change to a 40 watt halogen headlight.

Also you can change the tail light to an LED.

If you are using a small capacity (less than stock 14 amp/hr) battery, try a larger capacity battery.

For comparison, my stock alternator puts out 13 to 13.5 volts at 1200 rpm.
 
Okay so I'm running a 60/55w H4 auto bulb, which I will change. Also I checked voltage at each of the yellow wires and was only getting 5-6V at idle. Now to find out why. The battery is a 16a/h sealed.
 
Okay so I'm running a 60/55w H4 auto bulb, which I will change. Also I checked voltage at each of the yellow wires and was only getting 5-6V at idle. Now to find out why. The battery is a 16a/h sealed.

the voltage seems low to me at idle
When You checked the voltage on the three yellow wires at Idle,
lettering the wires A,B,C
did you measure using the AC setting?
did you measure A to B, B to C, C to A
Not trying to sound like a smartazz that's 3 different checks and all 3 were the same voltage?
Did you rev the engine during the tests?
If so what did the voltage rise to? should be around 50 volts AC.
I don't know what PMA you have but at idle the voltage should be higher than 5-6 volts AC
 
So when I checked the yellow wires coming off the pma I checked from each wire to ground. When I check between wires I get no reading. I get good continuity between yellow alternator wires as well. I forgot to check for infinite continuity between the wires and ground.
Am I supposed to check yellow wires for Vac with the regulator unplugged?

Should I be getting any reading between yellow and ground when running?(reg/rec plugged in?)
 
I have infinite resistance between ground and all 3 yellow wires. And to answer your question when revving i get up to 7 volts then it starts going down. Almost like my regulator is kicking in too soon or something.
 
So when I checked the yellow wires coming off the pma I checked from each wire to ground. When I check between wires I get no reading. I get good continuity between yellow alternator wires as well. I forgot to check for infinite continuity between the wires and ground.
Am I supposed to check yellow wires for Vac with the regulator unplugged?

Should I be getting any reading between yellow and ground when running?(reg/rec plugged in?)

You can indeed check the voltage coming off the stator while the engine is running with the reg/rec unpluged. In fact it is the easiest way to test the voltage you can get to the three pronged plug end and test.
Set your meter to AC voltage
your NOT testing from each yellow wire to ground.
You ARE testing yellow wire to yellow wire. With engine not running of course your not going to get voltage. So start the engine with the stator unpluged from the reg/rec.
your going to test A/B, then B/C, then CA check each at idle what the voltage is, then rev the engine and the voltage should raise with RPMs untill around 50 volts AC.
All three tests should be close if not the same on each A/B,B/C,C/A.
In this video the guy is performing th test I have described.
 
Okay so did the right test this time and have the same ~10v at idle and 20-30v when revving. No where near the 50v you speak of. Not sure where to go from here. I'll check the pma hopefully something's weird on it.
 
Okay so did the right test this time and have the same ~10v at idle and 20-30v when revving. No where near the 50v you speak of. Not sure where to go from here. I'll check the pma hopefully something's weird on it.
.
I was expecting the numbers to be higher. (I could be wrong Man) maybe banshee PMAs voltage wont go the high . they are made for off road quad runner. (I'll look into that today)
30 volts will surely keep you battery charged with no problem while running.
the 10 volts at idle wont.
Stock charging system don't really charge at idle either.
Any way is your battery going dead on you?
 
My pma is from xs650direct and I believe they get them from xscharge. 20-30v ac could very well be enough but having my battery below 12v is messing with my ignition and giving me a rough idle. The battery isn't completely dying but running off the battery at every red light is sure to pooch it quick.
What gauge wire should I be running to my terminals on my bat? I have 8 gauge on my negative and 12 on my posi.
 
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