Do I need to do some work on my alternator?

My turn signals have stopped blinking at idle. If I rev to around 1500 they come back on. My battery is sitting at 12.5 volts at idle, and goes up to 13.8 when I rev it.

I checked the resistance according to the Haynes book. On the white wires, I'm getting around .4 to .5 ohms. On the green and brown wires I'm getting a weird reading. There is a small m next to the reading. It's around 8 m ohms

 

Have you checked you alternator brushes? You might simply need new ones, they're easy to replace. They have wear line indicators, chances are that's all you need. Pull the cover off and have a look.

 

No, I didn't check the brushes. The cover is just up and to the left of the starter right?

 

Yep, just don't be too rough with it, where the wires are attached to the cover. You'll see what I mean.

 

The brushes are IN the cover.

The alternator doesn't "kick in" until about 2200rpm; below that it's on the battery to do all the work.

That being said, 13.8V is a tad low; you should be seeing 14.5V above 2K rpm.

Once the charging system checks out, if you still have issues it may simply be time for a new battery.

 

Bah, I hope it's not a battery. This is the second one this year

 

Also, what would cause the turn signal issue? As soon as I rev up to 1500 they kick back on...

 

Not having enough voltage from the battery alone to make them flash. As soon as you rev it up enough for the alternator to start adding to the available current, they flash.

If you're "eating" batteries then you do need to attend to your charging system (unless you've been letting them run dry...)

 

Another cause would be a faulty flasher relay.

 

If it were the relay it wouldn't suddenly work above 1500rpm.

The relay requires a certain amount of current to operate. Below the RPM at which the alternator starts to make any serious juice, the power for flashing the signals comes from the battery.

The immediate cause is a slightly weak battery; WHY the battery is apparently perpetually weak is the underlying problem.

The relay is not the problem. It is behaving appropriately.

 

The flasher has been replaced with the electrical flasher mod that is stickied somewhere.

I'll check my brushes later tonight. That spec should be in my Haynes, right?

 

Good call on the brushes. They are both pretty worn, one also had a broken lead.

 

Another thing to cross off the list.

And another good example of the fact that ANYTHING you overlook during a resurrection of a 30 year old bike WILL bite you at some point.

If you haven't replaced your original 30-year old brake lines yet, do it soon. From your list, they're now the weak link in the chain and you do not want to pop one under hard braking.

You're actually getting close to running out of stuff to attend to. Good job.

Now the polishing begins (if it hasn't already.)

 

Polishing?! You don't polish a rat bike!

I'm actually kinda liking the rough look, and think I'm gonna roll with it.

I still have the old brake lines. I'm planning on moving up to stainless pretty soon. I've just gotta take it easy on my bank account. I've got a 100 year old house I'm renovating too...

I'm thinking I might need to service my starter soon too...