Topic: System charging but have a constant drain somewhere. (Got to be the Battery)

[78 k550]

Hey All,
I killed 2 main fuses friday riding around. I made it home, put my meter on my battery only like 8 volts. I take a look at the point very pitted so I got a tune up kit. 30.00 I looked at the bottom of the battery and was corroded on the bottom. So I bought a new one. I charged then I put the battery in and 12.45 volt across the meter go riding all day and starter wont kick the bike over. and low volts on the battery. I put the battery on charger and got out the meter. Every thing checks good. Except when I run an ohm test across the alt. It should read 4.5 ohm's  I'm getting 1.0 ohm's, looks like time for a new Alt. Thats what the book and my troubleshooting tell's me I should swap. No grounds to any of the pins but Alt. is bad anyway. I have one off my  77 550F but the pin's are different. It reads 4.0 ohm's and the spare 72 I have is reading 4.5 ohm's. Time to swap out a Alt.
 Any thing else I should look for?
I figure I can just cut off my old harness off my old Alt. and splice in the round pins and reinsert them to the plastic plug.

Paul

[Paul]

Paul,
Did you check across the three phases of the "Alt" to see what AC Voltage you were getting...disconnected from the R/R and running.
other that that splice away...

[78 k550]

No I did not check it with it running other than the meter across the battery. It wont run with that plug disconnected will it? Not sure what you mean by R/R, to me that means remove and replace. Sorry not to clear on it. I'm still betting on the Alt. being bad. it has only 1 ohm and should be at 4.5 ohms.

TT, anything I should be doing different?

Paul

[TwoTired]

Are we discussing a cb550 or the 750?

It can happen, I suppose, but usually the rectifier expires before the alternator stator windings.
The Stator wires should be yellow.   Measuring resistance between any two of them ought to be around 0.35 ohms assuming a CB550.  That's a very small resistance some meters are incapable of measuring correctly.  Even then, operator technique can be the difference between good and bad measurements.  Describe your ohm meter.  Digital? analog?  Have you acounted for test lead resistance?
Crude measurements will usually suffice. Insensitive meters will likely read all the stator windings as shorted to each other.  But, none of them should have a connection to the engine case.

Next would be the field coil. The book says it should be 4.9 ohms, +/- 10%. across its white and green leads.  Disconnected from the bike, neither lead should have continuity with the engine case.  If your feild coil is indeed measuring 1 ohm then it is drawing twelve amps at the white wire instead of about 2.4 A, and a likely cause of main fuse cook off.

Usually checking alternator specifics is done after verifying that the battery isn't receiving a charge with the engine running.  This is done with a voltmeter on the battery.   But, if you can't keep a main fuse in there, that would explain why this hasn't been done.

If you fear your rectifier is shorted, causing the alternator to drain the battery, then disconnect the rectifier and use you ohmeter or DMM with a diode test setting, to check that each of the six diodes only has continuity with only one polarity of the test probes.

If you are confident that the feild coil is indeed measuring 1 ohm, that is a problem.

Cheers,

[78 k550]

Are we discussing a cb550 or the 750?

It can happen, I suppose, but usually the rectifier expires before the alternator stator windings.
The Stator wires should be yellow.   Measuring resistance between any two of them ought to be around 0.35 ohms assuming a CB550.  That's a very small resistance some meters are incapable of measuring correctly.  Even then, operator technique can be the difference between good and bad measurements.  Describe your ohm meter.  Digital? analog?  Have you acounted for test lead resistance?
Crude measurements will usually suffice. Insensitive meters will likely read all the stator windings as shorted to each other.  But, none of them should have a connection to the engine case.

Next would be the field coil. The book says it should be 4.9 ohms, +/- 10%. across its white and green leads.  Disconnected from the bike, neither lead should have continuity with the engine case.  If your feild coil is indeed measuring 1 ohm then it is drawing twelve amps at the white wire instead of about 2.4 A, and a likely cause of main fuse cook off.

Usually checking alternator specifics is done after verifying that the battery isn't receiving a charge with the engine running.  This is done with a voltmeter on the battery.   But, if you can't keep a main fuse in there, that would explain why this hasn't been done.

If you fear your rectifier is shorted, causing the alternator to drain the battery, then disconnect the rectifier and use you ohmeter or DMM with a diode test setting, to check that each of the six diodes only has continuity with only one polarity of the test probes.

If you are confident that the feild coil is indeed measuring 1 ohm, that is a problem.

Cheers,

Sorry, it's the 500 giving me the problem. Yes only 1.0 ohm out of the Alt. I'm Pos. of that. Should I go to the salvage yard and cut a harnes and utilize the pins and a little wire to splice over to the pin connectors? I'll call the yard tomorrow and see what Alt are going for.
The spare one I have riged up now is charging and seem's to be working. The old Alt. wasn't charging with a meter across the battery, only showing like 8 volts..

[78 k550]

Alt is or was putting out 62 a/c volt but swapped it anyway with one that has 4.5 ohm's. I talked to Tim and asked also what the A/c volts it is putting out. So he filled me in on how to check it. Not my problem. I think my battery is shot. It isn't holding a charge. it is only 3 or 4 days old I guess it could be bad. I'm charging it up now to get full power. If I just have the motorcycle battery hooked up it looses volts as I watch not with just the key on. I just noticed after I hooked up my car battery it isn't draining. I hope new battery I put in 4 days ago is bad, I have check wire's with a running 72 CB500 and it checks out the same. I just let the car battery sit for awhile and see if it take's (needs) longer for the volts to stop dropping. Well no drop in volts with the key on or off with the car battery hooked up.
I when over to checkers to return the battery and got another free only 3 days old. I ripped the red plastic strip off and was about to pour the acid in then noticed a few plates in a few of the cells contacting each other and they looked like they where starting to corrode. I went back and showed it to them I got another just as bad on the inside. So I got my money back and will never buy a Champion/Excide battery again. I'll try my luck with a Diehard or a battery from a local company called Batteries Plus.

Paul

[TwoTired]

I recommend you hold out for a Yuasa Battery.  The Yumicron variety has EDTA in it, which is a chemical that helps the battery recover from sulfation when it hasn't been charged for a while.

Also, the YB12A-A has larger (or more) plate area to help it withstand the rigors of Halogen headlights, etc.  However, it's outside dimensions are teh same as the standard battery for the bike.

Cheers,

[78 k550]

Thank's TT,
I'll definately check out the battery you mentioned.  I charged the Diehard battery last night and seem's to be holding a charge. I'm going on a ride for abit today so we shall see. It is great to learn about your electrical system the hard way when it was only the battery. Testing everything and trouble shooting it. I thought I knew my bike before.

Paul

[scout18]

Hey there I just was going through my own trouble shooting guide that I got form this site. It says to do a full load test first to determine batt. condition. Turn on the ignition and headlight with the bike not running if voltage across the terminals is less than 10.5 volts your battery is bad and needs help . If you have more than 10.5 volts, the battery is ok and you can do a rpm test. Start the bike and rev it to 4000 where you should have 14 -15 volts.