Alternator Charging Question...

Tor-King · March 25, 2017, 05:27:54 PM

Hi everyone!
I finally have taken out my '88 from hibernation. I acquired this bike last year and it had not been started for some 10 years. After a great number of hours to prepare for initial starting, the big day finally came. It fired up immediately and ran beautifully! The only thing that appears to not be working is the charging system. I have a new battery in it, fully charged (reading 12.6v). When I start it, the voltage at the battery drops to 12v. I checked the brushes and they are within limits (much greater than 4.5mm). I also took off the alternator to clean up the area a little better.
So here are my questions:
1. Where do I begin to check?? **where are some potential areas to look...
2. When I removed the alternator, it appears that some oil came out of the alternator drive shaft... is that normal??

Thanks guys!
Dean

FJ1100mjk · March 25, 2017, 07:11:43 PM

Check the two-pin, red connector that's attached to the alternator's wires. That connector is suspect for charging problems. You my find it corroded and/or melted.

A little engine oil found upon the removal of the alternator is normal.

PaulG · March 25, 2017, 07:36:10 PM

No.2 If it's more than a little oil, the seal may have dried up or shrunk after sitting idle for so long. After some extended heat gets into it it may swell a bit to quell any further leaking. Get a few runs on it so it goes through some heat cycles and recheck it if you can. If it hasn't changed then you will at least have peace of mind for the season. If not, then you can change it before the season gets into full swing.

If a charging issue and a potential minor oil leak is all you have to worry about after sitting for 10yrs, that's a bonus.

BTW new tires I hope?

Tor-King · March 25, 2017, 08:10:39 PM

Hello again.
FJ1100mjk:
The red connector is not melted and nor corroded...

Paul:
I will have a look again later to see if the seal is the culprit. Yes, new tires are in order and I am also amazed that the bike runs so well and needs so little. Next in line is brake and clutch master rebuilds...

Any other ideas as to the charging issue??
Dean

racerrad8 · March 25, 2017, 08:33:41 PM

On the bike side of the red plug.

One terminal should be constant battery voltage.

The other side should be ignition switched battery voltage.

If you have both of the proper voltages then something in the generator is bad. If you don't then it is on the bike side.

Yes, oil will come out when the generator is removed, the shaft splines are oil pressure fed.

Randy - RPM

Tor-King · March 25, 2017, 09:10:22 PM

Hi Randy!

This is what I discovered, obviously without the bike running...

Battery is fully charged and reading 12.99V

With the ignition OFF, one side of the red plug terminal is reading 12.99v and the other side is 0v
With the ignition ON, one side of the red plug terminal is reading 12.07v and the other side is 11.42v

What is your professional judgement?

Thanks,
Dean

FJmonkey · March 25, 2017, 11:19:32 PM

Did you check the red connector by pulling it apart? On my '89 it looked good on the outside, not so good on the inside...

simi_ed · March 26, 2017, 01:06:06 AM

It's that loose screw we've all been looking for!

markmartin · March 26, 2017, 09:09:20 AM

For me it was the red plug, as FJMonkey said, it only showed when I took it apart - and it was toast. But is sounds like you've been at it if you've tested both sides of it.

If all else fails, don't discount going through the wire harness looking for chaffed wires. I had a situation that would intermittently kill the bike when the RPM's dropped down to idle. I found a pinched wire going to the rear blinker that I think might have been grounding out. Anyway, the problem went away after I wrapped it in electrical tape.

racerrad8 · March 26, 2017, 11:24:55 AM

Quote from: Tor-King on March 25, 2017, 09:10:22 PM
With the ignition OFF, one side of the red plug terminal is reading 12.99v and the other side is 0v
With the ignition ON, one side of the red plug terminal is reading 12.07v and the other side is 11.42v

Dean

Dean,

Since you have battery voltage at both wires and it still is not charging, the problem is going to be from the red plug to the generator.

Broken wire
Melted solder joint
Bad Generator

It is going to take some more troubleshooting.

Randy - RPM

Tor-King · March 26, 2017, 11:56:48 AM

Randy,
I just checked the wires from the red plug to both connections inside the generator. Neither wire is broken (checked with meter) and solder joints all look good. I have another generator, from an '86. Can I try it on my '88?

In the shop manual it shows them as being slightly different:
output: through '87: 14v, 26A
'88 and later: 14v, 28A

stator coil resistance: through '87: .19 -.21 ohm
'88 and later: .15 - .18 ohm
Thanks,
Dean

moparman70 · March 26, 2017, 06:29:39 PM

I took one from an 86 model and put it on my 90 which is the same as an 88 so I will say Yes you can.

Also --- I have been troubleshooting a short and in my work I have been seen a few trouble spots. The RED connector on the left side from the alternator as you mention is one of them -- mine looked good from the outside but was all melted and ugly inside as Monkey had mentioned ---( not my issue but I corrected it all the same)

There is another area up under the tank by the goose neck that I am sure is the same power wires or a least maybe part of the circuit. I found mine to be heated as well in this area. It is a white 3 prong connector with a BROWN - and RED wire similar to the wires at the alternator. My Red popped out pretty easy. There is also a small blue wire as part of this connector.

I don't know if it is part of the cct you are dealing with but thought I would mention it as it could be a problem. ( still not my issue but like I said I was fixing things as I found them.

sc2

Tor-King · March 26, 2017, 07:24:25 PM

Hey Moparman!
The generator that was NOT working (on my '88) has good connectors, nothing melted and no broken wires. The one on my '86, the generator I was planning on trying on my '88 HAS melted wires on both sides of the red connector. So there you are, add me to the list along with Mark and others...

That is good news that the '86 generator will plug right in. The only thing I could see different, visually was the o-ring thickness. I will just need to fix up the wiring first.

Thanks!
Dean

racerrad8 · March 27, 2017, 10:52:27 AM

Quote from: Tor-King on March 26, 2017, 11:56:48 AM
Randy,
I just checked the wires from the red plug to both connections inside the generator. Neither wire is broken (checked with meter) and solder joints all look good. I have another generator, from an '86. Can I try it on my '88?

In the shop manual it shows them as being slightly different:
output: through '87: 14v, 26A
'88 and later: 14v, 28A

stator coil resistance: through '87: .19 -.21 ohm
'88 and later: .15 - .18 ohm
Thanks,
Dean

As Steve already said, yes the alternators will interchange. The only difference will be two and three bolt flanges.

Randy - RPM

Tor-King · March 28, 2017, 08:31:33 PM

Well, the generator was the problem all along. I installed a generator from an '86 onto my '88 and everything is a go. Charging nicely but maybe on the high side in terms of voltage. At 2500 - 4000 RPM it is charging anywhere between 14.6v - 15 v. It jumped up to 15.1v at one time. Will this cook the battery with the generator cranking out these volts? According to Clymers it is within specs for it to be charging up to 15.3v, but I feel that that is on the high side? Opinions?

Thanks,
Dean

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